1. Dominance hierarchies in male lizards: Implications for zoo management programs
2. ; A critical reanalysis of the ontogeny and phylogeny of mammalian social and locomotor play: an ethological hornet's nest. Pp. 296–337 in Behavioral Development. The Bielefeld Interdisciplinary Project. , , , eds., Cambridge, Cambridge University Press, 1981.
3. The energetics of reptilian activity. Pp. 155–199 in Biology of the Reptilia. Vol. 13. , eds. London, Academic Press, 1982.
4. Learning processes in reptiles. Pp. 555–681 in The Biology of the Reptilia, Vol. 7 (Ecology and Behavior). , eds. New York, Academic Press, 1977.
5. On the origins of play. Pp. 1–41 in Play In Animals and Humans, ed. London, Basil Blackwell, 1984.