How do you find useful sources on a topic you want to research? It can be easier than you realize! I usually use the following methods when looking for books and articles to support my research, and they tend to help make documenting a project much easier. Of course just because something is in a book that doesn't mean it is automatically a good things to cite - books can still have inaccuracies, especially if they are older or written for a less-academic audience - but having a variety of options is an excellent thing!
1. Local library (public or university). As I am a faculty member mundanely I use my university library, but public libraries are amazing too! For example, my local library, Salem Public Library, shares a network with several universities and public libraries all over the state and can get me any book in the network for free. Look at the websites of the libraries in the city or town you live or work in and see what they have. My local library also has access to multiple online scholarly journals and databases too, many of which I can access online just using my library card number.
Once I find the library catalog, I then start looking for keywords relating to my topic (for my project this meant keywords like "16th century," "16th Century Italy," "Renaissance Fashion," etc.). Many of these books might not be exactly what your topic is on, but they can often have chapters or sections that do touch on the topic. This can be a great way to find books that maybe have a different focus but that may still have useful information (such as a great book on Venetian textiles that talked about the difference in fabrics popular in Florence versus Venice). If there is an author I was told is good I also look to see if they have written anything else on the same topic.
Additionally, the librarians may be able to assist you with your research! Let your librarian know the topic you are looking to learn more about and they may be able to assist you with your online searches and by looking at other resources the library may have access to.
2. Online Recommendations. There are many Facebook groups and websites for such a variety of topics - 16th century clothing, Norse tablet-weaving, 14th century metalwork - these can be great resources for finding books that are respected and considered helpful. For Facebook groups look in the files section for book lists, search the page for the topic, or post asking for recommendations. Search for websites on the topic that have a research focus and see what books they cite. Look if other people in the SCA have posted their documentation online and see what is cited there. For example, in tablet-weaving Peter Collingwood's book The Techniques of Tablet Weaving is probably the most commonly cited source, so that might be a great book to look into trying to track down if you wanted to learn more on the topic (either through your local library, buying used online, or borrowing). In general, looking at what good sources cite can be a wonderful way to find more useful sources, be they listed in the works cited/bibliography of a book, article, someone's SCA documentation, or a website.
3. Online Journals. This may vary slightly depending on the access to journals you can get through your local library. Journals are shorter articles published in the academic world on a variety of topics and can be a wonderful resource, looking at archaeological digs, museum finds, analyses of medieval texts, and more. Academia.edu is a free resource and therefore highly recommended to all, but if your library has access to other journals, periodicals, or other indexes of scholarly articles they can certainly be worth checking out - if you aren't sure where to start this is a great topic to ask the librarian about.
Archaeological Textiles Review has their older editions available to download for free (great resource if you are a fiber researcher), and other specialty journals sometimes do the same. Google Scholar is a search option that looks at scholarly articles and citations, which can be a wonderful way to find sources but it can be a challenge to get access to all of the articles or books you may see. Google Books can be a great way to see all or part of a book online - if you can't get access to the entire book you can sometimes see the chapter headings to let you know if the book could be a good investment.
4. WorldCat. This is a bit more of a challenge, but it can be helpful if you are not getting enough results using the other methods. WorldCat is a giant online catalog of books and articles held in libraries all over the world. You can search by subject, author, titles and more. It will then show you books and what libraries they are in nearest you. This can be very upsetting when you find the perfect book but it is only available in Paris, but it is a very handy tool nonetheless. If there is an amazing book at a university or other private library within driving distance you can always call or e-mail the librarian asking if you can visit as an independent researcher to take notes on a specific book they own. While some libraries are more limited, many will allow anyone to come in to look at books, especially with prior permission from the librarian. Worldcat can also be a great way to find books that you may want to request via Interlibrary loan (a way that libraries share books with each other) if your library has that as an option. Additionally, you can always check how much the book costs to purchase online once you find the title and author, or ask around if anyone has a copy that you could borrow.
5. SCA Network. The SCA is filled with many people with incredibly diverse interests, so they can be an incredible source of information on obscure topics that you might be having trouble with. Contact your local A&S minister, post a question to your Kingdom's Facebook group or e-mail list, ask around if anyone knows someone working on that topic. There is a wealth of information out there that people love to share.
While there are many other options too, these tend to be my go-to methods for finding sources on a new topic. Especially for earlier SCA periods where research may be limited, having a broader base to draw on can make the documentation process much easier and can dramatically improve your depth of knowledge in a field.
As mentioned above, please do keep in mind that not all books are always correct - for more information about determining if a book or article is likely to be a good option to cite see my guide How to Research Like an Academic.
As always, if you have any questions or comments please e-mail me at firstname.lastname@example.org!