Took some time to go through all your sketchbook, and youve really improved over time. You conceptualization of masses is becoming finer and finer. You also have great rendering techniques. Only thing i would could suggest is to try to draw the forms more as u seen them modeled in your head and not to rely only on what you see on the model. For example: i love the profile portrait you did of your friend (Dec. 8th) but the dark tone on the bottom of her face takes away from the illusion of form and draws the eye downwards. Maybe you could have subdued it a little?
Your anatomy studies are awesome (both drawn and molded), and i cant wait to see where you'll take them. Post more soon!