You have the Southern Slavs, in what would eventually be referred to as the Balkans. And then you have the Eastern Slavs, in what will eventually be Russia, Belarus, and Ukraine. Now to be clear, they weren't unified groups. There were many, many, many, for example, Eastern Slavic tribes. Our best account of the early history, especially in the period as we get into the ninth century, comes from what is known as the Russian Primary Chronicle. And keep in mind, this was written at a much later period. It was written in the early 12th century.