One additional information:
When Christianity came into the lands and declared belief in old gods paganism, they couldn't erase existence of the gods so they renamed them.
So god Perun became Sv. Ilija, there is in Croatia mountain peak called Sv. Ilija which in the history held the name of Perun.
The others i don't recall but there must be some writings about that.
There are no records because they used old gods as a parallel to saints, and for the easier absorbtion. For example I ve found a reference that says st. Nicholas was compared to Veles because of the simillar apperance and Veles wealth and water aspect