In 1939, he obtained his engineering doctorate with a thesis on surge voltages, and was appointed assistant professor at the university.

In 1854 he obtained his doctoral degree with a thesis on galvanometry.

He obtained here the title of doctor of philosophy with a thesis on Kant (1848).

He obtained his doctorate in 1957 with a thesis on Vincent van Gogh.

He obtained his doctorate with a thesis on the muscles and bones of dinosaurs.

In 1931, he obtained his doctorate with a thesis on the Volta effect.

He obtained his doctorate in 1978 with a thesis on the quantum mechanics of black holes.

In 1906 he obtained his doctorate with a thesis on the nephridia of polychaetes.

Zimmer obtained his doctorate in 1934 with a thesis on photochemistry.

In 1875 he obtained his doctorate with a thesis on the urogenital organs of reptiles.