Ronald Slaby and Karin Frey (1975), p. 854.
71
Carolyn Edwards (1993), p. 327.
72
William McGrew (1992); Elizabeth Lonsdorf et al. (2004); Stephanie Musgrave et al. (2020).
73
Beatrice Ehmann et al. (2021).
74
Suzan Perry (2009).
75
Frans de Waal (2001); Frans de Waal and Kristin Bonnie (2009).
76
Axelle Bono et al. (2018).
77
Aaron Sandel et al. (2020).
78
Ashley Montagu (1962) and (1973); Nadine Weidman (2019).
79
Melvin Konner (2015), p. 206.
80