Hm, this is bery interesting. But there is no yugoslavian language, just serbian,croatian, slovenian, bosnian, macedonian and so on. We anno used the "serbian-croatian" dictionary when needed. But these are different languages.
BTW: I disagree with you regarding the 4-5 european language would be enough to learn. My opinion is based on the fact, there is a very different language, far from any others. I'm Hungarian :-)