Many thanks to the reference sources for helping me with my studies. Some of the sources I've mentioned below, about the others I have no idea... wish I could credit them as well. But I'm sincerely indebted to all.
Refs by kind courtesy of Croquis Cafe, New Masters Academy youtube channels, and unknown others. Fourth from below is courtesy of Cinnomanangel in Deviantart (model) / Eric Boutilier-Brown (photographer). Thank you!