R. Bruce Williams 
Cooperative Learning [PDF ebook] 
A Standard for High Achievement

Cooperative Learning reveals some of the structural complexities involved in implementing authentic cooperative learning in the classroom. It also suggests that when full cooperative learning structures are implemented, the benefits in student achievement often can be astounding. Descriptions, decisions, designs, and developments, a simple four-part scheme, introduce and refine the skillful use of cooperative learning in the K-12 classroom.