Ramphastos vitellinus culminatus - Yellow-ridged Toucan

Chapman, F. M. 1924. Auk: 41(1): 17-29.
Criteria for the Determination of Subspecies in Systematic Ornithology

No Author Listed. 1933. Auk: 50(3): 381-384.
The Ornithological Journals

No Author Listed. 1971. Auk: 88(1): 187-201.

Pearson, D. L. 1971. Condor: 73(1): 46-55.
Vertical Stratification of Birds in a Tropical Dry Forest

Davis, T. J. 1986. Condor: 88(1): 50-56.
Distribution and Natural History of Some Birds from the Departments of San Martin and Amazonas, Northern Peru

Avise, J. C. and C. F. Aquadro. 1987. Auk: 104(2): 324-328.
Malate Dehydrogenase Isozymes Provide a Phylogenetic Marker for the Piciformes (Woodpeckers and Allies)