Edwin George Lutz

https://archive.org/stream/whattodrawhowtod00lutz#page/n0/mode/2up
http://archive.org/stream/drawingmadeeasyh00lutz#page/n0/mode/2up
https://archive.org/stream/practicalartanat00lutz#page/n0/mode/2up
https://archive.org/stream/practicaldrawin00lutzgoog#page/n8/mode/2up
https://archive.org/stream/cu31924075701304#page/n0/mode/2up

Viktor Hertz

http://www.viktorhertz.com/

Nathalie Parain

http://crean.es/nathalie-parain/
http://atelierpourenfants.blogspot.com.es/2010/04/ronds-et-carres.html
http://rocketlulu.typepad.com/objets-vintage-curiosites/2013/05/page/2/