I was asked by Heitler to act as a sort of interpreter between him and Majorana. He spoke hardly any Italian, and Majorana's German was a bit weak. So during lunches, Heitler expressed a curiosity in what Majorana was doing; Fermi must have told him how bright he was. So Majorana began telling, in that detached and somewhat ironical tone, which was typical of him, especially when discussing his own work, that he was developing a relativistic theory for charged particles. It was not true, he said, that the Schrödinger equation for a relativistic particle had to have the form indicated by Dirac. It was clear by now, that in a relativistic theory one had to start from a field theory and for this purpose the Klein–Gordon wave-equation was just as legitimate as Dirac's. If one took that, and quantized it, one got a theory with consequences quite similar to Dirac positron theory, with positive and negative charges, the possibility of pair creation etc. You can see what I am driving at: Majorana had the Pauli–Weisskopf scheme all worked out already at that time. […] Heitler probably forgot all about it, and so did I, until I saw the paper by Pauli and Weisskopf.

I must confess that I knew enough to understand the gist of what he was saying, but not enough to appreciate how novel and original it was. Heitler probably did, because his comment, as I recall it, was: “I hope you will publish this.” […] [But] in the case I have described publication never occurred. [299, 300]