http://www.earnedschedule.com/Docs/April%2019_Earned%20Schedule_Walt%20Lipke.pdf
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.113.1740&rep]=rep1&type=pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/a567071.pdf
https://www.apm.org.uk/media/1233/earned-schedule.pdf
https://www.pmiwdc.org/2015/12/pm-tools-workshops
http://www.pmknowledgecenter.be/sites/default/files/files/Vanhoucke%20et%20al%2C%20TMN%2C%202015.pdf