1. Why do some bird species feed in flocks?;Murton;Ibis,1971
2. Wilson, E.O. (1975) Sociobiology: The New Synthesis, Harvard University Press
3. Williams, G.C. (1966) Adaptation and Natural Selection, Princeton University Press
4. Geometry for the selfish herd;Hamilton;J. Theor. Biol.,1971
5. On the advantages of flocking;Pulliam;J. Theor. Biol.,1973