Kloosterman was appointed lector (associate professorship) at  Leiden University in 1930 and full professor in 1947. In 1950 he was elected a member of the Royal Netherlands Academy of Arts and Sciences.
The passage describes Kloosterman's academic career milestones: his appointment as an associate professor at Leiden University in 1930, his promotion to full professorship in 1947, and his election as a member of the Royal Netherlands Academy of Arts and Sciences in 1950.