References to litterature and data
Enigma (Danish Museum for Post, Tele and Communication) - Photos of archival material
Tofdata 7.05 by Lasse Nielsen - DOS database about Matrice and Galvano flaws all values
Selandia 81 (National Exhibition catalogue) Page 61 to 68 by Lars Peter Svendsen - Matrice and Galvano flaws 3 sk
NFT year 109 no 4 December 2002 by René Kjelskov Jørgensen - Matrice and Galvano flaws 2 sk