Question:
Where was Hendrik Kloosterman educated in Sep, 1921?

Context:
 Hendrik Kloosterman attended University of Hamburg from Jan, 1927 to Jan, 1928. 
 Hendrik Kloosterman attended Leiden University from Jan, 1918 to Jan, 1924. 
 Hendrik Kloosterman attended University of Göttingen from Jan, 1926 to Jan, 1927.

Answer:
Leiden University