I've never been one to fill up sketchbooks. However, when I suffer the occasional 'artist's block' between projects, I'll get out my magazines, or my Michelangelo & Da Vinci books, and do a few drawings from those, just to keep my skill level up. Alternatively, I'll photograph a friend, and draw them ( as is the case with the PORTRAIT OF SIMA, below ).
Above: Portrait of Sima ( preparatory drawing ), 2011
Below: Portrait of Sima ( detail ).
Below: Portrait of Minty
Below: Assorted sketches from books.