I'm trying to find some information about my father's parents family. His name was Rajko Kalaba - he was born in Mahovljani (I think in Serbia?) on 16th Sep 1939. At some point the family moved to Banja Luka. His parents were Simo and Stana, and I believe they both died in WW2 - we think they are listed on the Jasenovac website, but I am aware that doesn't mean they died in that camp (ie the disclaimer). All my father ever said was that they died during the war.
I believe that Simo's parents names were Petar or Paro, and Jovanka or Joka.
Is there any way to contact someone about births or deaths records, or census records from these areas? (has to be in English).
Anyway, I would appreciate some advice as to how to go about finding out more information. Particularly about how and when my grandparents died, and information about their parents. Please note that I am in contact with some of my father's relatives over there, but his sisters are quite elderly now and cannot speak English.