Adzerak's book o' sketches

[Fedodika]

From what i can see in your recent work you keep making the same mistakes with the structure of the head/proportions,form etc. I think you've pushed yourself as far as you can efficiently go without some observation to supplement your efforts.

I'd reccomend getting used to laying in the planes of the face correctly for one, make sure the features arent sliding into no mans land, and practice just generic lay ins to make sure you get the perspective right from every angle. Also learn neck anatomy, and how the sternomastcloid leads in from the front and the trapezius from the back.

Try hampton, hogarth and loomis head drawing methods my man best of luck!

Oh and as far as photo studies, just simplify the planes of the face from photos after you've done some of the above stuff, dont worry too much about features like noses eyes etc. just placement