1. A critical reanalysis of the ontogeny and phylogeny of mammalian social and locomotor play: an ethological hornet's nest;Bekoff,1981
2. Social ecology and behavior of coyotes;Bekoff;Adv. Study Behav.,1986
3. On the origins of play;Burghardt,1984
4. Precocity, play and the ectotherm-endotherm transition;Burghardt,1988
5. Terrain preferences in the play of Siberian ibex kids (Capra ibex sibirica);Byers;Z. Tierpsychol.,1977