Go to [link]http://towerhobbies.com[/link]. Use their menu on the left and click on "books and vidieos".

They have two books on aerobatics: "Great Planes a look at Aerobatics" by Mike Cross and "Aerobatics for Everyone" by Dave Patrick.

They also have a video featuring Chip Hyde covering basic aerobatics.

The book by Mike Cross looks promising as it has diagrams included.

Hope this helps.