1. R. J. Antor, 2001 .Conservation strategies for the recovery of the bearded vulture in north-eastern Spain during 1998-2000 .Pages21 -30inA. Sakoulis, M. Probonas, and S. Xirouchakis, editorsProceedings of the Fourth Workshop of Bearded Vulture Crete Natural History Museum of Crete and University of Crete, Erakleio, Crete.
2. Effects of Population Density and Supplemental Food on Reproduction in Song Sparrows
3. J. Bertran, and A. Margalida .1996 .Patron anual de observaciones de Quebrantahuesos (Gypaetus barbatus) de diferentes grupos de edad en los sectores de nidificacion .Alauda,64:171 -178.
4. J. Bertran, and A. Margalida .2002 .Territorial behavior of the Bearded Vulture (Gypaetus barbatus) in response to the Griffon Vulture (Gyps fulvus) .Journal of Field Ornithology,73:86 -90.
5. Temporal, spatial and social segregation of red-billed choughs between two types of communal roost: a role for mating and territory acquisition