- The Ultimate Sales Machine: http://www.amazon.com/gp/product/1591842158/ref=as_li_ss_tl?... - Spin Selling: http://www.amazon.com/gp/product/0070511136/ref=as_li_ss_tl?...

and this is a very good article on the general topic:

http://blog.teamtreehouse.com/sales-lessons