Art Gainz https://pilssken.neocities.org/gainz/
Art Tutorials Wiki http://artwiki.wikidot.com/
Line of action https://line-of-action.com/
DrawingFORCE https://www.drawingforce.com/
Drawspace https://www.drawspace.com/
PSG Art tutorial https://androidarts.com/art_tut.htm
Digital Painting & Concept Art http://www.floobynooby.com/ICG/artvalues.html
Egg a Zyotatsu http://www.eggazyoutatsu.net/eng/atarichanDrawer.html
Ctrl+Paint https://www.ctrlpaint.com/
Hitokaku (JP) https://www.asahi-net.or.jp/~zm5s-nkmr/
Iradukai (JP) http://iradukai.com/
Open Drawing Books https://drawingbooks.org/index.html
Loomis https://alexhays.com/loomis/
Doxy Tutorials https://prismblush.com/tutorials/