conceptual thinking/sketching books

I am open to suggestions of books teaching techniques to work through design issues with sketching.

ive got a copy of this book from Umea its filled with some amazing sketches and step by step breakdowns of how they were drawn. It covers a mixture of digital and marker type sketches.

also, Scott Robertson’s how to draw cars the hot wheels way is pretty good

I also have the design sketching book, and my school made it a text book/reference for our visualization class… I would highly recommend this book…

thanks guys.

I actually have that book and did not realize that it was required reading.