Over at Painters Table there have been some interesting posts on drawing and the portrait: Ingres, Philip Pearlstein, Paul Housley, Freud, Lorenzo Lotto. Very little is mentioned these days of Sickert, or Gilbert Spenser, Mathew Smith, or Keith Vaughn.
Painting the head, that closest of observation, is a fascinating commitment. John Rothenstein opined that it shouldn't be done too often but looking at Rembrandt's recurring visage suggests that there is much to learn by so doing.
On my table at the moment is a monologue on the Israeli artist Avigdor Arikha. Because I never learned to paint the head I need to look at a range of good work and I am grateful for Painters Table, and for books of course.