In early October of 1939, designated by the government as the year of "the duty to be healthy," Hitler authored a secret memo certifying that "Reichsleiter Bouhler and Dr Brandt are hereby commissioned to allow certain specified doctors to grant a mercy death [Gnadentod] to patients judged incurably sick, by critical medical examination."
p. 177 - Racial Hygiene: Medicine Under the Nazis, 1988