I have found the website of a marvelous portrait sculpter, Philippe Faraut.
He teaches sculpture, does forencic reconstruction, and sells sculpting supplies.
If you click on reference casts, then click on the small thumbnail which comes up, a full size picture of the cast appears. On my monitor the pictures are about 10" in height, and clear.
There are... planes torsos, facial features (eyes noses etc), planes of the face and head, skull, masks depicting fear, sadness, discust, anger, rage, smile, surprise, child, youth, adult, maturity, and antiquity (a 90 year old).
He also has a fine portrait gallery. I have seen a few videos on youtube, of him creating some of the sculptures. I think that this is a great resource for drawing, and I hope it helps people like me, who are self learning.
The website is called PCF Studios.
Other sites I have found with images are,...giustgallery.com and pafa.org