Jun 2022

It's now 2 years since I started down the rabbit hole that led to Hands Down (first with Notarise). I'm still using Hands Down exclusively (Rhodium, a.k.a. Neu-rx+), and really couldn't be happier. I have been super busy writing all sorts of academic papers, tens of pages per day, and teaching online (typing real time in both English and Japanese). Every Hands Down variation on this site for at least a week, to get a feel for its performance. They're all so much better than QWERTY it is ridiculous. 

A host of other new layouts have appeared since I started this. I've tried many of them out, and many are also extremely good! I still much prefer the Hands Down typing sensations and rhythms, but there are so many other great options that it is a good time be jumping the QWERTY ship and doing your joints a favor.

I finally got to working on an implementation on ZMK, and posted links for my current draft. My QMK code has matured, and an update there will come when I have time.

I'll plan to do some work on the Hands Down Polyglot project while in France for a research year. Already my nascent ability and initial French corpus analysis and typing have shown exceptional results.

Happy Typing!

Oct 2021

There's a new Discord Server for Hands Down here

July, 2021: The review of my notes this summer has led me to rediscover some previously explored but unfinished avenues of research. These included some notes about rolling and stats for punctuation, and an early, primitive exploration of what is now known as Adaptive Keys. Spurred on by these findings, I developed new layouts, Hands Down Élan, and Hands Down Neu, then Hands Down Gold,  Silver and Bronze. They are still just close enough to the core Hands Down Home Block that I consider them part of the family, but they are all another notable step ahead in many ways. 

This verbose website has served as the training ground for typing on each new layout. First the Hands Down Reference layout, then Hands Down Alt, Hands Down Alt-tx/nx, Hands Down Élan and now Hands Down Gold. I think the Hands Down theories and variations are now very close to tapped out. and there is a complete family of layout options that have a high degree of coherence, even with their many differences. After you have become comfortable with one of variation in the Hands Down family, it should take considerably less time (a week or two) to become proficient with another of the variations, should your interest or needs change. Hands Down variations are definitely mature enough to heartily recommend as suitable for daily use. I still strongly feel that the best layout is the one that feels comfortable to the individual typist, so you should use the one that makes the most sense to you, whether that is a Hands Down variation, or something else.  

May, 2021: It was Labor  Day, 2020: The thought of designing a layout hadn't crossed my mind when I tried Workman on my new Redox, just after passing my literature PhD qualifying exams (on a newly built Kyria that I still use). A few weeks later I had designed Notarise, becuase Workman wasn't working for me, then a few weeks after some very helpful feedback, I posted the first request for feedback on Hands Down. After some interest, I created this website initially to facilitate wider peer review as the work evolved. Hands Down has now matured a bit, and I'm aware of some errors/discrepancies in my documentation throughout this site (documentation/stats/layout JSON files, etc). That's not exactly surprising, since this whole project is new, done while a full-time graduate student and teaching demanding language courses.

It's time to tidy things up. I will soon begin the last phase of reviewing all my notes and logs, and comments from others. I will update this site and all the layout information when I can. The result of this review will certainly be very close to what is here, but some slight changes could be made to the layouts themselves, so it might be best to consider everything here as a very late stage beta version. (Don't expect much change to the home-block—3x3 under index, middle, ring+pinky & thumb resting positions—as that sort of defines "Hands Down", but do expect things to be more polished and consistent throughout.)

Hands Down "1.0"—the peer reviewed, edited, time-tested version—will be finished sometime this summer; but I'm still in school, and teaching an intensive accelerated language course this summer, so it will be some time before I can give it it the focused attention it deserves. I hope then to finish all the study across various keyboard types, KLAs, producing the definitive versions of KLA JSONs, and finalizing the native OS support for Linux, Mac OS, and Windows.

Very special thanks to all who've given Hands Down a try, and have reached out to offer comments—this has most certainly helped improve the design, helped me be more accurate with my documentation, and have identified errors that I now get to correct.

Let me be clear…
Home Row Mods are a choice for comfort,
not for speed.

Hands Down is designed to take ergonomic keyboard design further, being specifically designed for small, split ergonomic keyboards with home-row modifiers in mind. Solving the problem of damaging lateral force that occurs when the the pinky must hold down shift key, or the thumb is curled under the palm to press down and hold a modifier, is a critical component of any comprehensive ergonomic solution. Hands Down does work well on ortholinear (a.k.a. matrix) (i.e. Planck, Preonic, etc.) and even traditional row staggered keyboards (see OS support for traditional keyboards on the downloads page). It is simply inspired by modern split ergo keyboard designs.

Hands Down extends the logic of relieving the deforming lateral forces on the pinkies and thumbs, being specifically designed for small split ergo keyboards with a deliberate thumb cluster and column stagger and uses layers (...like Absolem, Atreus, bat43, Corne, Gergo, Iris, Keyboardio, Kyria, etc..and possibly any Ergodox, Dactyl or manuform variant).  Hands Down aims to improve comfort and performance by reducing hand movement away from home row even for shift, ctrl/cmd, alt, as well as for layers such as navigation, numbers, fkeys, media key etc. 

Harmful static lateral force from holding modifiers is the primary reason to consider home row modifiers, but many layouts already burden the index and middle fingers with such high frequency letters that the added burden of home row modifiers creates inefficient overuse. Mod placement and the layout itself must be designed together, including considerations for finger frequency, dexterity, and neighboring letters in shortcuts. By considering the impact to home row fingers taking up the ctrl/alt/cmd/shift work previously done by the pinkies, the layout and keyboard together produce more comfortable typing.

 Hands Down was designed specifically for ctrl/alt/cmd/shift (CAGS): Shift on index, cmd/ctrl on middle, and Alt always on ring fingers.  In concert with my Semantic Keys, cmd/ctrl would swap middle/pinky, according to platform.  This is one of the main reasons why Hands Down avoids overburdening the index finger, to reserve capacity for the busy shift work. If you are serious about considering Home Row Modifiers, I recommend you check out this page by Precondition for a thorough, technical discussion of home row modifiers. Cmd/ctrl on middle-finger allows for many easy one-hand shortcuts, and shift on index works well with opposite hand shift to balance the load and reduce misfires.

Mana Harbor's Miryoku project helps to manage home row mods with Colemak-DH and Dvorak, and some other layouts. Ironically, the word miryoku (魅力) is Japanese for "charm," or "beguiling," but Colemak just didn't captivate me, though Miryoku does. It could be that Colemak expected too much of my index fingers (with the added burden of home row mods), or because it was uncomfortable for me when typing  in Japanese, where K is very common. But Miryoku is very smart and thorough, and worth a look.

Hands Down does play well with shift on thumbs

Home Row Mods are not for everyone, and they do have drawbacks. The big drawback is timing control for multi-use keys, and that can have a significant  impact on typing speed. Callum Oakley's style of "one shot" modifiers or a mod layer like Seniply by SteveP99 (Colemak-DH designer) are also excellent ways of handling modifiers on small keyboards, and these approaches work quite well for some. 

But you can also just keep the modifiers where they are. In fact, all the tests for stats mentioned here were done with shift on thumbs, for all layouts and keyboards tested, because none of the analyzers I used were able to consider multi-use keys required for home-row mods.  I used shift on thumbs for months before designing Hands Down. Shift on thumbs doesn't have the delicate timing issues that mods on home have, and still keeps the pinkies out of harm's way. It's totally worth implementing Hands Down this way (on backspace and enter, for example, but not recommended on space). 

For me, because of the frequent need to combine shift with other mods and having only one thumb, and my very heavy use of combos for my multi-lingual work, I went for the home-row mods route after months with mods on thumbs. It's not without issues, but I'm now quite comfortable with it, and definitely prefer it to shift on thumb, let alone on the pinky.  With careful attention to settings, home-row mods work very well, and the stats get better across the board. I don't aspire to being a competitively fast typist, so all my design decisions are made for long duration comfort typing (~80wpm sustained for long periods of time).

What about ALL_CAPS for keywords and acronyms? Holding shift while pressing multiple keys is particularly harmful to the weak pinkies. Obviously, simply pressing both L+R shift = CAPS_WORD, a super-fast, logical "more shift,  until the end of the word please." Of course, regular caps_lock is available by pressing the two keys adjacent to the L+R shift  combo. Gone are the days of strange contortions trying to string along three or four caps together while holding shift with a pinky because caps_lock is so inconvenient, right there on home row with everything else, literally right under your fingertips.

Thumbs up for Happy Pinkies

The first step to freeing pinkies from their keyboard purgatory is to move the shift and other modifiers so the pinkies won't suffer from constant lateral pressure. Any keyboard and layout should work together to reduce the physiological strains that arise from using them in ways that stress the fingers by optimizing for each finger's attributes.

All Hands Down variations deliberately try to distribute finger burden roughly aiming to slightly favor the index and middle fingers in different ways; while producing a functional balance between the critical same-finger bigrams (SFB), neighbor-finger bigrams, and individual finger usage frequency.   Hands Down prime directive is to burden fingers according to their various strengths and weaknesses, more than to achieve some statistical objective (stats are used heavily, but only to the realize the prime directive). Hands Down follows a fingers-first design philosophy:

• Index fingers are dextrous, but it still takes time to travel farther to cover 2x the number of letters, and that movement displaces the entire hand for inner column keys.  It may not be wise to overload the index finger with the highest usage frequency, even if the SFBs are low. 

• Middle fingers are strong, so they get focused, high frequency repetitive tasks. 

• Ring fingers, though stronger than the pinky, are typically the least dextrous, not normally accustomed to moving independently. (Row jumps are the worst on ring fingers. Combos in unison with neighbor fingers are OK, but independent movement is hardest on these.)

• Pinky is weak, and the most susceptible to joint damage from lateral forces  (like holding a shift key down). 

• Thumbs are neither dextrous nor fast, nor are they well suited to lateral forces such as that on a typical keyboard hitting the space key, but it is strong. I find any more than 3 thumb keys to contribute to thumb confusion, as with new ergodox layouts with so many thumb keys that may expect too much dexterity of these brutes. 

• Hands Down Neu/Gold and esp. Titanium/Rhodium/Vibranium with H Digraph combos offer exceptionally low pinky and middle column usage. Like, stupid-crazy low, with similarly insanely low SFBs.

Nota Bene: Many BEAKL layouts are specifically designed to minimize pinky use, and may be ideal if reducing pinky use is your primary concern, or you choose to keep the mods on separate keys near the pinkies. There's a lot to like in many of the BEAKL layouts, but some take the pinky allergy to such lengths that I think the result may be sub-optimal. On the other hand, if you have a pinky injury...these may be ideal!

 What makes Hands Down click?

I'm going to write some stuff here about how I prioritized letter placements for Hands Down.  If you already know how layouts are designed, then what follows will likely be tedious. 

Hands Down was not developed by algorithms*,
and was definitely tested on human(s)†.

If you are wanting information to help you choose a new layout, knowing that layout choice usually involves a sizable commitment of time and effort, you may find this unapologetically verbose philosophy narrative worth your time, whether you end up choosing a Hands Down variation, Hands On, or any other layout. I do hope this will help you learn indirectly the reason's why QWERTY is fundamentally flawed, and help you find something better. There are very good alternatives that are readily available on most operating systems (Dvorak, Colemak, Workman). Native OS support for Hands Down Reference, Alt, Neu (and Hands On) is in the works. All these layouts have many differences, even if they score similarly on one analyzer or another. You should be able to understand the differences in order to choose (and maybe adapt) a layout to suit your typing style, physical keyboard, hand physiology, and even personal preferences.

Most new layouts have a design philosophy blurb, and, frankly, they all sound so similar that they sort of lose their value. They tend to talk about why QWERTY is bad, and how it is good to do this or that thing while typing (alternating hands, rolling fingers motions, reduced movement, etc.). There's nothing inherently wrong with these statements, it's just that at the blurb level, what we're all wanting is the same thing—more comfortable, efficient typing. But there are big differences in how a layout realizes that goal. Many times those high level goals are in such conflict that they are rarely achieved, and the choice of physical keyboard itself is as important as the layout you put on it. That's why I've been so verbose in all the other sections that are aimed at a specific facet of the design principles, or with a bit of design story, so you can understand it from a how point of view, rather than abstracted philosophical statements that might end up sounding like any other high-efficiency layout.  Here I will try to be clear about the what drives the design decisions of the Hands Down layout and its variations that might be different than the common goals shared with other designs; but I will explain it with practical examples of how it is manifest in the Hands Down design. I may draw contrasts with other layouts here, but in no way do I mean it to say Hands Down is therefore better (except for QWERTY). I know Hands Down is very good, but so many other layouts are also very good, just in different ways, and they may be better for you.

First, some terms I've used throughout this website: 

• Same-finger bigrams (SFBs). This one is, unquestionably, the single most important design consideration. For this reason, and because it comes first, this will be the longest of the sections. Same-finger bigrams, (SFBs) are letters sequentially typed by the same finger. It is crucial that this number be as low as possible, and a meticulous attention to SFBs is the basis for Hands Down's exceptional statistics. QWERTY has very high SFBs, 1/2 of which occur on the left middle finger with the letters EDC. E is the most frequent letter, by far, so it should never come anywhere near any other high frequency letter; E should be isolated as much as possible.  The worst thing would be for a SFB to require a jump over the home row, as is required for the common bigrams CE (#43, bottom to top) and  EC (#61, top to bottom) on QWERTY. It's rather ridiculous. The Hands Down Reference layout has a mere 1/6 the SFBs that QWERTY has (84% less), much lower than most other layouts, and that is something you will feel very, very quickly.
  But there are many factors that affect letter placement, and it might be that a slightly higher SFB on some fingers may be better than simply having the absolute lowest SFBs possible. TH, for example, is by far the most frequently occurring bigram in English, so low SFB logic says that they should be on separate fingers.  Q and U, on the other hand, have the highest co-occurrence ratio of any letter pair (they almost always appear together), so they too, should be on different fingers, no? These two bigram pairs are obviously very different. TH is very frequent as a bigram and both T and H are high frequency letters on their own, but Q and U occur less frequently, which is not much at all. Clearly, low SFB for QU doesn't have the same importance as it does for TH. Similarly, SFB and finger placement are different. The bigram WR is much less common than QU, so wouldn't it make sense that the WR bigram might be better on weaker/less dextrous fingers than the QU bigram, even if W and R each are more common on their own than Q or U? It's easy to see that which finger you place a bigram on (making it a SFB) matters a great deal, and every layout will have many of them. Some of them will inevitably be awkward.
  Consider the phrase "The Buddha didn't write bland scripture." † The highlighted bigrams occur with very different frequency, and are placed on fingers accordingly.  Th (#1) and nd (#10) occur so frequently that they are never on the same finger. (nt (#24) is separated by apostrophe, so it's not considered a SFB in this case.) The bigrams wr (#293) and cs (#273) are much less common than TH, so although awkward when encountered, they are tolerated on the same finger. Nevertheless, every effort is made to make typing SFBs in the most common sequence as easy as possible (CS is more common than SC, WR is more common than RW), which generally means "raking" toward your body, from top to mid, or mid to bottom rows. What about QU, then (#163), which though more common than WR, occurs less frequently than most double consonants (LL #46, SS #74, EE #88, TT #149)? On most Hands Down variations, Q is realized via combos with the same sounding letter, K, with U on the adjacent finger, so Qu is almost a SFB because of the combo, but it feels about like typing a double letter, and given its high co-occurrence, it behaves as such.  In Hands Down practice, typing Qu  is almost faster than if it were on separate fingers. TH vs QU is an extreme contrast, used to illustrate the point. There are dozens of other similar choices that are much less obvious, that I hope to illustrate in the sections below. 
  You may have noticed that before I've addressed all the terms, I've already mentioned many of them while discussing SFBs. This is because any consideration cannot be made in isolation of the others for a truly usable layout. Paying attention to any one factor, even critical SFBs, to the exclusion of the others will almost inevitably result in a suboptimal layout with some very awkward motions. Truly great layouts strike some sort of balance  between these competing priorities. There are many such layouts that do strike a very usable balance, though they will feel very different when typing on them.

† (The Buddha didn't write any scripture, and neither did Jesus, Lao Tsu or Socrates) 

• Home Block vs Home Row vs: 3x3 block of keys on each hand, 3 keys for each of the index, middle, and ring fingers, and the home/resting positions for the pinky and thumb, and you have the 22 keys that define the prime real estate for keyboard design. The inner column key next to the index finger is harder to reach than any of these Home Block keys, even though it is on home row. And since the pinky is the shortest finger, it has more difficulty reaching the upper or lower keys. Hands Down is designed with an almost obsessive attention to these 22 locations, and awareness of the fingers that govern them. Even among these 22 prime spots, no two are equal in terms of effort. This effort map is also different between keyboard types (traditional, ergo, ortholinear, etc). It's a Monopoly board game, of sorts, with Boardwalk and Park Place going to the most frequent letters: E and T (or N, depending on the variation). Consider the keys that are outside this 22 key "residential" area (Monopoly has 22 "residential" streets where you can build housing), including the two keys above or below the pinky's home position, and the entire center column on each hand, to be the Rail Road or public utility spaces — necessary, but you don't want to live there. 

• rolling, raking, pushing,  skipping, jumping, and reaching:

  • Rolling in vs out; Inward roll are undeniably better, but outward rolls are inevitable. The goal is to make the outwards rolls be less common, or at least have the higher frequency rolls occur on more capable fingers. Sadly, many layouts still have IO, a very high frequency bigram, rolling outward on the outer ring to pinky fingers. On Hands Down, OA is on the ring on pinky,  more common than AO, but it is an outward roll in order to make the common IO bigram possible on the more dextrous index to ring finger roll and to optimize the most common vowel rolls OE, OU, for very comfortable inward rolling on the most capable fingers. Hands Down Polyglot optimizes for more inward vowel rolls, at the expense of slightly higher SFBs.

  • raking down vs pushing up (SC vs CS; GS vs SG; UI vs IU)

  • Skipping rows on neighbor fingers is harder than skipping fingers. (RL, GH, CH, MB, LB, BL easier than SM, SL)

  • Jumping rows (GL not ideal, but CL more common, so managed w/GM combo)

• Top vs Bottom row? Is it better to Stretch or curl? Should you stretch your fingers to reach the top row, or curl your finger under to hit the bottom row? Your keyboard, finger lengths, and other factors can influence how you type, and what is most comfortable to you. The top row over bottom row habit of many layouts is another QWERTY holdover, as it was designed to favor the top row in order to keep the fingers close to the number row for telegraph operators (this is why UIO are on the top row, not the hoe row, having been swapped for JKL), and to keep the levers shorter for more responsive mechanical action. None of these factors are relevant in modern computer keyboards.  
  I learned four decades ago in jr. high type class, and thirty years ago from an ergonomist that Apple had hired to consult on workplace ergonomics, that a proper finger curl and floating hands utilizes the more capable flexor muscles vs RSI prone tensor muscles, so my typing habit involves curled fingers and a preference for the middle and lower rows.  (Apple bought my first split-ergo keyboard for me in 1993. And I learned that WRIST WRESTs ARE BAD! it compresses the carpel tunnel!) This lower row habit works great since I don't use a number row (I use a 10-key layer),  so proximity to a fourth row is not important for me, and I have slightly shorter middle-to-ring finger ratios than the average.
  I prefer split-ergonomic column staggered keyboards,  which also cater to this flexor vs tensor preference. The four (or eight) keys outside the home block are less sensitive to their neighbors, but all were thoroughly evaluated for these specific positions while developing all Hands Down variations. The comfortable rolls of most Hands Down variations are the product of these neighbor-finger relationships. On ortho-linear keyboards, it may be better to swap the top and bottom keys of the inner column, to accommodate the natural angle that the hands approach the keyboard. This may also  be true of the  top and bottom pinky keys. This "wrist splay" is a major source of RSI, and why I've not used a traditional (or ortho-linear) keyboard regularly in over 25 years.

• Frequency/distance distribution/balancing:

  • Middle more frequency, 

  • index more distance (lower frequency to accommodate greater distance)

  • Ring is least dextrous (move together w/ neighbor fingers whenever possible, esp. w/chording)

  • Pinky more independent than ring, but weaker, so a bit more distance, w/low total frequency/

  • Thumb is all thumbs: not nimble, so bad for mods...1 layer at a time, plus space/letter.

• static pressure/lateral force: 

• combo/chording:

Sources: 

• Baker NA, Moehling KK, Park SY. The effect of an alternative keyboard on musculoskeletal discomfort: A randomized cross-over trial. Work. 2015;50(4):677-86. doi: 10.3233/WOR-131797. PMID: 24284689.

• Grudin, Jonathan T.  and Larochelle,  Serge, "Digraph Frequency Effects in Skilled Typing", Cognitive Science Laboratory, University of California, San Diego https://apps.dtic.mil/sti/tr/pdf/ADA112926.pdf

• Marklin RW, Simoneau GG. Design features of alternative computer keyboards: a review of experimental data. J Orthop Sports Phys Ther. 2004 Oct;34(10):638-49. doi: 10.2519/jospt.2004.34.10.638. PMID: 15552709.

• Rempel D, Barr A, Brafman D, Young E. The effect of six keyboard designs on wrist and forearm postures. Appl Ergon. 2007 May;38(3):293-8. doi: 10.1016/j.apergo.2006.05.001. Epub 2006 Jun 27. PMID: 16806042.

• Rempel D. The split keyboard: an ergonomics success story. Hum Factors. 2008 Jun;50(3):385-92. doi: 10.1518/001872008X312215. PMID: 18689043. https://pubmed.ncbi.nlm.nih.gov/18689043/

• Swanson NG, Galinsky TL, Cole LL, Pan CS, Sauter SL. The impact of keyboard design on comfort and productivity in a text-entry task. Appl Ergon. 1997 Feb;28(1):9-16. doi: 10.1016/s0003-6870(96)00052-x. PMID: 9414336.

The "Standard" keyboard is harmful

The Blickensderfer model 5 of 1902 had only 32 "keys," if you include the carriage return arm as a key. Somewhere in the hundred and twenty years since, we've only made thing more difficult by adding almost one new key per year, and not given equal attention to the hands that use them. Some of Hands Down's exceptional stats are directly attributable to its small keyboard heritage, approximated on the layout analyzers. The result of all this is more comfort and more speed–less space is just a welcome bonus. (My Ingulish layout posts incredible stats with only 28 keys.)

Where is TAB? Semicolon? More combos (chording, sort of like stenography, only simpler): Just press QC for TAB (QW on QWERTY), ,+.=;, j+'=", ./= \.. You get the idea, there are many more of these, and they are actually easier to reach than on a separate key.  Full navigation and numpads, function keys and special symbols for programming or linguistics—all are embedded right beneath your hands in easier to understand and easier to reach positions than on a larger keyboard. These layers are accessed by the thumbs, which is why mods went to the home row.  Swapping mods and layers does work, btw (layers on home row, mods on thumbs), but I find it much less stress on my joints to have the thumb do the layer switching. 

I`ll eventually write more about my research into the physiological factors of keyboards here. Until then, here is a non-exhaustive pasteboard of various articles.

 I have over 100 combos on my 34 key keyboard, meaning I have the equivalent of much more than the "standard 101 key keyboard. I also use layers for organization and workflow efficiency, so my small keyboard can produce all the symbols and commands that any other keyboard can, but it is generally easier to remember and faster to access with combos. Since combos require pressing two (or more) keys at once, the switch spring weight can become more noticeable—I've used lightweight springs (35g or less) in my keyboards for this reason.

• Check out this engaging video about how small keyboards "work" 

• Here's a personal story about switching to split ergonomic keyboards.

• KBD.News: See what funky new designs are emerging at Keyboard Builder's Digest.

• John Helveston created a very slick Split Ergo Keyboard comparison tool that can help you choose a keyboard that fits you.
  Find a split ergonomic keyboard to fit your hands, rather that force your hand into a one size-doesn't-fit-any-well. 

References:

1. ---Effect of Wrist Posture on Carpal Tunnel Pressure while Typing. Journal of Orthopedic Research. 2008 Sep; 26(9): 1269–1273. doi: 10.1002/jor.20599

2. Baker NA, Moehling KK, Park SY. The effect of an alternative keyboard on musculoskeletal discomfort: A randomized cross-over trial. Work. 2015;50(4):677-86. doi: 10.3233/WOR-131797. PMID: 24284689.

3. Grudin, Jonathan T.  and Larochelle,  Serge, "Digraph Frequency Effects in Skilled Typing", Cognitive Science Laboratory, University of California, San Diego https://apps.dtic.mil/sti/tr/pdf/ADA112926.pdf

4. Marklin RW, Simoneau GG. Design features of alternative computer keyboards: a review of experimental data. J Orthop Sports Phys Ther. 2004 Oct;34(10):638-49. doi: 10.2519/jospt.2004.34.10.638. PMID: 15552709.

5. Rempel D, Barr A, Brafman D, Young E. The effect of six keyboard designs on wrist and forearm postures. Appl Ergon. 2007 May;38(3):293-8. doi: 10.1016/j.apergo.2006.05.001. Epub 2006 Jun 27. PMID: 16806042.

6. David Rempel, The Split Keyboard: An Ergonomics Success Story, Human Factors: The Journal of the Human Factors and Ergonomics Society 2008 50: 385 DOI: 10.1518/001872008X312215

7. Swanson NG, Galinsky TL, Cole LL, Pan CS, Sauter SL. The impact of keyboard design on comfort and productivity in a text-entry task. Appl Ergon. 1997 Feb;28(1):9-16. doi: 10.1016/s0003-6870(96)00052-x. PMID: 9414336.