34 Hagen, The Secret Front. The view that Canaris's fears also played a part is put forward by Maurer in his memorandum. Hitler's statement that Heydrich went to Prague as his 'Duke of Alva' was made by Otto Meissner in Staatssekretar unter Ebert-Hindenburg-Hitler. The visit to the Fuhrer's headquarters mentioned in the text below is described by Schellenberg, Labyrinth. On the Himmler-Heydrich relationship see Labyrinth; also Hagen, The Secret Front, and Gerald Reitlinger, The SS, Alibi of a Nation.