1. Alcock J (1989) Animal behavior, 4th edn. Sinauer, Sunderland, MA
2. Auden WH (2000) Lectures on Shakespeare. Princeton University Press, Princeton
3. Borrello ME (2005) The rise, fall and resurrection of group selection. Endeavour 1:43–47
4. Buiatti M (2004) Il benevolo disordine della vita. UTET, Torino
5. Coco E (1994) Cronosofie naturalistiche. Coscienza Storica, pp 10–12