
all national core provinces for Serbia, Montenegro, Croatia, Bosnia and Slovenia have Yugoslavian cores added.all national core provinces have Yugoslavian cores added.or they're owned by a South Slavic nation who's on good terms with you assuming neither of the above is true, you need to either have their cores or their owner needs to be in your sphere.
if they've been released as a result of Great War dismantling, nothing else matters.if Serbia, Bosnia or Croatia exist and you're both in the same sphere, nothing else matters.
This may look complicated, but what it means is:
Croatia exists and is either in the same sphere as your sphere owner or has just been released by a Great War OR all Croatian national cores are either owned by you, their owner is in your sphere or their owner is South Slavic and has relations of 100 or better with you. Bosnia exists and is either in the same sphere as your sphere owner or has just been released by a Great War OR all Bosnian national cores are either owned by you, their owner is in your sphere or their owner is South Slavic and has relations of 100 or better with you. Serbia exists and is either in the same sphere as your sphere owner or has just been released by a Great War OR all Serbian national cores are either owned by you, their owner is in your sphere or their owner is South Slavic and has relations of 100 or better with you. May be formed by: Any member of the South Slavic culture group