So I'm looking for sources to read about early medieval South Slavic entities, not necessarily kingdoms. Curious about the cultures of the regions: mythology/lifestyle/warfare etc, before South Slavs became dominated by various foreign powers; Byzantium, Hungary, Austria, Venice, the Ottomans etc. Are there any good books, or art pieces, or anything? Most of the early/late medieval era seems missing for the South Slavs, at least here in the west it's almost impossible to find anything that shows our cultures at the time.

I blame this on foreign occupation, even several American and British professors have said South Slavs had rich cultures in the era, before subjugation. A real shame.

Look here, one can find interesting stuff.