Obviously, the book about Royal Yugoslav Air Force appeared in Serbia in 2012, and sold out. Maybe here You can by it:
http://ng2.sone.ovh/spletna-prodaja/...ile-1918-1944/
The book had about 650 pages with hundreds of photos, list of all units and their commanders as well as short chapters about Serbian Aviation and Aviation of National Councils as their predecessors.
kind regards
Newcomer