For a free and readable book on Direct Instruction, go to:

http://education-consumers.org/ClearTeaching.htm

Written by Shep Barbash and commissioned by Education Consumers, Clear Teaching is a short manual on Direct Instruction and Zig Engelmann. On the page are links to other documents such as a trainers list and various other DI resources.

http://thetartan.org/2011/8/29/scitech/psych

"The researchers’ review highlighted a conflict in the current approaches to early science schooling. Educators on one side argue for a more hands-off methodology. They claim that preschoolers go through a natural flow in scientific cognitive development — a flow that should not be interrupted by explicit teaching. Another approach stresses exactly the opposite philosophy — that, essentially, early intervention via direct instruction can help children develop a rudimentary understanding of the complex concepts involved in scientific reasoning."