Where can I find in-depth coverage of the physics behind slipstreaming/drafting?

I have been searching all over the internet for information on the physics behind slipstreaming or drafting, such as calculating the optimal distance an object should be behind another in order to experience the least drag. All I have found are a couple of Wikipedia articles as well as short automobile, biking, and swimming web-pages that briefly cover the subject. If anyone could post any links or other resources, I would be very appreciative.