1. Ainsworth MDS, Blehar MC, Waters E et al. (1978) Patterns of attachment. Erlbaum, Hillsdale, NJ
2. Baerends GP (1976) The functional organization of behaviour. Anim Behav 24:726–738
3. Bell AM (2007) Animal personalities. Nature 447:539–540
4. Block J (1977) Advancing the psychology of personality: Paradigmatic shift or improving the quality of research. In: Magnusson D, Endler NS (eds) Personality at the crossroads. Wiley, New York
5. Bowlby J (1969) Attachment and loss, Vol. I: Attachment. Hogarth Press, London