Complex sentence: Most of historians (Franjo Rački, Nada Klaić, Lujo Margetić, Neven Budak) point at Croats, Ivo Goldstein at Byzantines, while Nenad Labus refers to this event as a successful assassination attemp by Avars and Slavs.
Split into simpler sentences: Most of historians (Franjo Rački, Nada Klaić, Lujo Margetić, Neven Budak) point at Croats, while some like Ivo Goldstein point at Byzantines. Connecting these two events, Nenad Labus refers to this event as a successful assassination attemp by Avars and Slavs.