Complex sentence: After the World War II the Soviet Union transferred Abrene and Abrene District back to Pskov Oblast, which has been a matter of Latvian-Russian disagreement since the collapse of the Soviet Union.
Split into simpler sentences: After the World War II the Soviet Union transferred Abrene and Abrene District back to Pskov Oblast. This annexation has been a matter of Latvian-Russian disagreement since the collapse of the Soviet Union.