Правда, в статье 1929/30 года Дирак ошибочно отождествляет такую дырку с протоном: "We are therefore led to the assumption that the holes in the distribution of negativeenergy electrons are the protons."
Но уже в статье 1931 года он исправляется:
"Subsequent investigations, however, have shown that this particle necessarily has the same mass as an electron and also that, if it collides with an electron, the two will have a chance of annihilating one another much too great to be consistent with the known stability of matter."
(+сноски — H. Weyl, Тамм, Оппенгеймер, Дирак).