Complex sentence: Machinsky is particularly well known for having excavated Lyubsha and other Viking settlements along the Volkhov River, which he ascribed to the Rus' Khaganate, whose capital--as he believes--was Ladoga.
Split into simpler sentences: Machinsky is particularly well known for having excavated Lyubsha and other Viking settlements along the Volkhov River. Machinsky ascribes these settlements to the Rus' Khaganate, whose capital--as he believes--was Ladoga.