After brief stays in Göttingen and Leipzig, he went to Copenhagen on 8 April 1930 to work at the Niels Bohr's Institute for Theoretical Physics. He stayed there until 3 May of the same year. After the visit, Landau always considered himself a pupil of Niels Bohr and Landau's approach to physics was greatly influenced by Bohr. After his stay in Copenhagen, he visited Cambridge (mid-1930), where he worked with Paul Dirac, Copenhagen (September to November 1930), and Zürich (December 1930 to January 1931), where he worked with Wolfgang Pauli. From Zürich Landau went back to Copenhagen for the third time and stayed there from 25 February until 19 March 1931 before returning to Leningrad the same year.