Answer based on context:

According to German casualty lists quoted by The Times for July 30, 1945, from documents found amongst the personal effects of General Hermann Reinecke, head of the Public Relations Department of the German High Command, total German casualties in the Balkans amounted to 24,000 killed and 12,000 missing, no figure being mentioned for wounded. A majority of these casualties suffered in the Balkans were inflicted in Yugoslavia. According to German researcher Rüdiger Overmans, German losses in the Balkans were more than three times higher - 103,693 during the course of the war, and some 11,000 who died as Yugoslav prisoners of war.

What was the profession of the person that provided the number of Germans lost in the Balkans during the course of the war?
researcher