Osterbrock, D. E. (Sep 2002). "Walter Baade, Dynamical Astronomer at Goettingen, Hamburg, Mount Wilson, and Palomar Observatories". AAS/Division of Dynamical Astronomy Meeting #33. 33. Harvard Univ: 10.03. Bibcode:2002DDA....33.1003O.
Baade, W. and Minkowski, R., 1954. Identification of the Radio Sources in Cassiopeia, Cygnus A, and Puppis A. Astrophysical Journal, Vol. 119, p. 206-214 (January 1954) ADS: 1954ApJ...119..206B