I like to support local products first:
Dave Robson's book, Aerobatics: Principles and Practice A good read is "Aerobatics" by Neil Williams - an oldie but a classic. The next book to buy, if you're getting into competitions, is
Better Aerobatics by Alan Cassidy
CASA's draft Manual of Standards identifies the knowledge requirements, for example:
- positive & negative g limits
- rolling g limits
- engine limitations
- phyiological effects eg G-LOC
- symptoms of an aircraft overstress
- Va, Vne & Vno
- minimum altitude
Have a look at what the MOS says about spinning - you'll need to understand the basics of spinning and reasons for the recovery actions.
I belive that there is a Citabria available at Sheparton, not sure who the instructor is. Give Pip Borrman a cal, I'm sure that he'd be happy to advise you.