I never paid much attention to faces. Never had the reason to. I am doing a portrait study right now. I didn't want to stress myself too much, so I picked pretty girls to study. They have problems. The eyes are uneven. The nose grows to the left. The lids are not symmetrical. When the mouth is closed a front tooth is sticking out. A really long face... I'm not going to talk about the bodies, but you get the picture. I need a book. Or a guide. What would you recommend?