Bosna province capital name

[Porca E]

I never heard of "Bosoj" in my career as historian.
Bosnia in Middle Ages had 4 documented royal centers: Vranduk on river Bosna, Jajce on river Vrbas, Podvisoki on river Bosna and Bobovac castle.
I assume that the rightful term here would be Vranduk.

 

[Mattius]

I know nothing of this region's history, but a quick Wikipedia check backs you up.