https://en.wikipedia.org/wiki/Golden_ratio
http://cityte.ch/y9
https://practicaltypography.com/
http://www.oercommons.org/courses/creative-typography/view
https://openlibrary.org/works/OL8247653W/The_universal_penman
https://archive.org/details/ArtOfThePrintedBook14551955
https://archive.org/details/ColesStephen.TheAnatomyOfType2012
https://archive.org/details/StrizverIlene.TypeRules.EnhancedEdition2014