I have to say beforehand that I don't know much about Slavic countries (I have some good articles on Poland, but not Bohemia or Serbia). Turkey & especially Mongolia would be easier - I have some friends who dig deeply indeed on these. I personally am more interested in Ancient Greece and Hellenistic world, though, of course, I have some information on Russian developments.
Plus European Renessaince (mostly Germany and England), and I have also information on China and surrounding regions, particularly Korea.