Letter from Edward Neville da Costa Andrade to Ronald Winckworth, on two papers 'The diffraction of sound pulses I. Diffraction by a semi-infinite plane' and 'The diffraction of sound pulses II. Diffraction by an infinite wedge' by Frederick Gerard Friedlander Recommends against publication during wartime, as it may have an 'important bearing on the design of protection against blast'. A mathematical referee should be consulted. [Both papers published in Proceedings of the Royal Society A, 1946]. 5 April 1940