Relativistic equations in quantum mechanics
pp. 320-330
in: Jagdish Mehra (ed), The physicist's conception of nature, Berlin, Springer, 1973Abstract
Let me begin by recalling the way I learned about Dirac's relativistic equation of the electron. It was from a letter to Max Born who asked Dirac to review an article by a third person. The letter started with this review, pointing out that two of the chapters could be united and that this would render the article more concise, that is shorter, and also easier to read. It had a few more remarks on the article in question. Then, in a new paragraph of about ten lines he said that he had been working on the relativistic theory of the electron. He gave his four-component equation, including the interaction with an electromagnetic field.