Referee's report by Charles Galton Darwin, on a paper 'On relativistic wave equations for particles of arbitrary spin in an electromagnetic field' by M Fierz and Wolfgang Ernst Pauli Sectional Committee: Mathematics Not recommended for publication in the 'Proceedings of the Royal Society of London'. Has not studied spinor calculus in detail. The results in the paper are so complicated the theory appears unprofitable. 'There would not be more than five or six people in England who would, or perhaps could, read it'. Refers to work of Paul Adrien Maurice Dirac. The paper is a follow-up to one recently published in Switzerland, and should most likely be accepted there. 'In fact, though the [Proceedings] should be open for publications of foreigners now debarred from Germany, I feel that any taken in that way should be rather exciting,, and I do not feel that this one is sufficiently so'. [Published in the 'Proceedings of the Royal Society of London'] Endorsed on recto as received 29 June 1939. [June 1939]