Complex sentence: Petrescu-Comnen soon joined the National Liberal Party (PNL) Constantinide--according to Constantinide, he owed his appointment to diplomatic office to his political connections.
Split into simpler sentences: Petrescu-Comnen soon joined the National Liberal Party (PNL). Petrescu According to Constantinide, Petrescu-Comnen owed his appointment to diplomatic office to his political connections.