Some human head study, well i use mostly western people as reference but it doesnt make much of a difference, later ill post more on study of human faces. Most probably racial facial distinction.
I know i left out some things like the human ear. Well its not difficult to know how to draw human ear but need to be able to draw it accurately but thats neglegible at times.
Im using a drawing technique which doesnt need to use much reference but the awareness and familiarness to help you draw without to have yourself looking at pictures and copy them exactly, with this you can draw the faces at any angle you want without having an exact reference. It helps with drawing comics most of all.
The real life ppl i draw here, i never copy them exactly from a picture but just look at a few references and draw them at my own choosen angle.