J. Grinnell, 1926, _Condor_, Vol. 28, p. 97 (robin). W. H.
Bergtold, 1930, _Auk_, Vol. 47, p. 571 (robin). H. W. Henshaw,
1921, _Condor_, Vol. 23, p. 109 (California woodpecker). D.
Bannerman, 1933, _Birds Tropical West Africa_, Vol. 3, p. 415
(thick-billed honey-guide).