Complex sentence: Kurt Horstmann of the Federal Statistical Office of Germany wrote the forward to the study endorsing the work of Reichling, an employee of the Federal Statistical Office who was involved in the study of German expulsion statistics since 1953.
Split into simpler sentences: Kurt Horstmann of the Federal Statistical Office of Germany wrote the forward to the study endorsing the work of Reichling. Reichling was an employee of the Federal Statistical Office who was involved in the study of German expulsion statistics since 1953.