21. [Cynopithecus niger] Publication: Bethesda, MD : U.S. National Library of Medicine, National Institutes of Health, Health & Human Services, 2009 Subject(s): HaplorhiniEmotions -- physiologyFacial Expression
22. Chimpanzee disappointed and sulky Publication: Bethesda, MD : U.S. National Library of Medicine, National Institutes of Health, Health & Human Services, 2009 Subject(s): Pan troglodytesEmotions -- physiologyFacial Expression