Complex sentence: Organization of the Petroleum Exporting Countries (OPEC,), a permanent, international organization headquartered in Vienna, Austria, was established in Baghdad, Iraq on 10--14 September 1960.
Split into simpler sentences: Organization of the Petroleum Exporting Countries (OPEC,), is a international organization headquartered in Vienna, Austria. OPEC was established in Baghdad, Iraq on 10--14 September 1960.