Quoted by Heiden, Adolf Hitler, Vol. 7. See also Frank, Im Angesicht des Galgens, who remarks:
'Gruber gave an essentially phrenological opinion, deducing both an absence of objective brainpower from Hitler's singularly receding forehead and an intellectually exceedingly subjective character from his strong occiput. Racially, Gruber characterised Hitler as typically un-Nordic, East Slav.'