"Five death sentences were confirmed: the sentence against Oswald Pohl, as well as those passed against the leaders of the Mobile Killing Units, Paul Blobel, Werner Braune, Erich Naumann and Otto Ohrlendorf. ... In the early morning hours of 7 June, the Nazi criminals were hanged in the Landesburg prison courtyard." Norbert Frei, Adenauer's Germany and the Nazi Past: The Politics of Amnesty and Integration. Columbia University Press, 2002. p. 165 and p. 173
books.google.com
Sereny, Gitta (1974). Into That Darkness: From Mercy Killing to Mass Murder (2005 paperback ed.). London: Pimlico. p. 97. ISBN978-0-7126-7447-8. Sereny also mentions the story in her 1995 biography of Albert Speer:
Sereny, Gitta (1996). Albert Speer: His Battle With Truth (1996 paperback ed.). London: Picador. p. 272. ISBN978-0-330-34697-9.