Lettera da Max Bohm a Albert Einstein, 5 aprile 1923
“I had Heisenberg here during winter (as Sommerfeld was in America); he is at least as talented as Pauli but is a nicer and more pleasant person.[11] He also plays the piano very well. Apart from the helium research, we examined some principal issues of Bohr’s atomic theory together, particularly regarding phase relations in models of the atom”