Historical question

[O'Hea]

I'm working on an alt history mod focused on warfare 1500-1700, and as part of the alt history approach I've decided to include Serbia and Rumania as playable factions. I'm having a lot of trouble finding any resources on the subject, since they were both occupied by the Ottomans during most of this timeframe, and I was wondering if any of y'all had knowledge in the field, or knew of some good books or websites on the subject.

Thanks,
O'Hea