Andigena nigrirostris nigrirostris - Black-billed Mountain-toucan

W. S. 1915. Auk: 32(4): 515.
Chapman on New Birds from Central and South America

Bancroft, W. D., E. M. Chamot, E. Clyde and C. W. Mason. 1923. Auk: 40(2): 275-300.
Blue Feathers

Ridgely, R. S. and S. J. C. Gaulin. 1980. Condor: 82(4): 379-391.
The Birds of Finca Merenberg, Huila Department, Colombia