1. Brauze, T. and Zieliński, J., The possibility of application of Sorensen and Renkonen indexes in the study of winter avifauna in small plots of the urban green areas, Ecol. Quest., 2008, vol. 10, no. 1, pp. 57–61.
2. Källander, H., Nilsson, S.G., and Svensson, S., The Swedish Winter Bird Census Programme, Pol. Ecol. Stud., 1977, vol. 3, no. 1, pp. 77–88.
3. Verner, J. and Milne, K.A., Analyst and observer variability in density estimates from spot mapping, Condor, 1990, vol. 92, no. 2, pp. 313–325.
4. Rosenstock, S.S., Anderson, D.R., Giesen, K.M., Leukering, T., and Carter, M.F., Landbird counting techniques: Current practices and an alternative, Auk, 2002, vol. 119, no. 1, pp. 46–53.
5. Nankinov, D., Attempt at censusing Corvidae and diurnal birds of prey in winter, Pol. Ecol. Stud., 1977, vol. 3, no. 4, pp. 189–192.