Ankel, F. 1970: Einführung in die Primatenkunde. Grundbegriffe der modernen Biologie Band 6. Gustav Fischer Verlag, Stuttgart.

Biegert, J. 1963: The evaluation of characteristics of the skull, hands, and feet for primate taxonomy. In: Washburn, S.L. (Ed.): Classification and human evolution, pp. 116-145. Aldine Publishing Company, Chicago.

Biegert, J. 1973: Dermatoglyphics in gibbons and siamangs. In: Rumbaugh, D.M. (Ed.), Gibbon and siamang, vol. 2, pp. 163-184. Karger, Basel and New York.

Blainville, H.M.D., de 1841(?): Ostéographie ou description iconographique comparèe du squelette et du système dentaire des cinq classes d'animaux vertébrés récents et fossiles, pour servir de base à la zoologie et à la géologie. Primatès. Atlas. Vol. 1. Arthus Bertrand, Paris.

Blyth, E. 1844: Notices of various Mammalia, with descriptions of many new species: Part I. - The Primates, Lin. Journal of the Asiatic Society of Bengal, Calcutta 13: 463-494.

Brockelman, W.Y., Reichard, U., Treesucon, U. & Raemaekers, J.J. 1998: Dispersal, pair formation and social structure in gibbons (Hylobates lar). Behavioural Ecology and Sociobiology 42: 329-339.

Carpenter, C.R. 1940: A field study in Siam of the behavior and social relations of the gibbon (Hylobates lar). Comparative Psychology Monographs 16: 1-212.

Chivers, D.J. 1974: The siamang in Malaya. A field study of a primate in tropical rain forest (Contributions to primatology vol. 4). Karger, Basel and New York.

Chivers, D.J. 1977: The lesser apes. In: Prince Rainier III of Monaco & Bourne, G.H. (Eds.): Primate conservation, pp. 539-598. Academic Press: New York.

Dal Pra, G. & Geissmann, T. 1994: Behavioural development of twin siamangs (Hylobates syndactylus). Primates 35: 325-342.

Dielentheis, T.F.; Zaiss, E. & Geissmann, T. 1991: Infant care in a family of siamangs (Hylobates syndactylus) with twin offspring at Berlin Zoo. Zoo Biology 10: 309-317.

Eimerl, S. & DeVore, I. 1969: Die Primaten. Time-Life International, Holland.

Fleagle, J.G. 1999: Primate adaptation and evolution, second edition. Academic Press, San Diego & London.

Geissmann, T. 1989: Multiple births in catarrhine monkeys and apes - A review, Editrice "Il Sedicesimo", Firenze.

Geissmann, T. 1991: Reassessment of age of sexual maturity in gibbons (Hylobates spp.). American Journal of Primatology 23: 11-22.

Geissmann, T. 1993: Evolution of communication in gibbons (Hylobatidae), Ph.D. thesis, Anthropological Institute, Philosoph. Faculty II, Zürich University.

Geissmann, T. 1994: Systematik der Gibbons. Zeitschrift des Kölner Zoo 37: 65-77.

Geissmann, T. 1995: Gibbon systematics and species identification. International Zoo News 42: 467-501.

Geissmann, T. 1999: Duet songs of the siamang, Hylobates syndactylus: II. Testing the pair-bonding hypothesis during a partner exchange. Behaviour 136: 1005-1039.

Geissmann, T. 2000: Gibbon songs and human music in an evolutionary perspective. In Wallin, N.L.; Merker, B. & Brown, S. (eds.), The origins of music, MIT Press, Cambridge, Massachusetts, pp. 103-123.

Geissmann, T., 2002a: Duet-splitting and the evolution of gibbon songs. Biological Reviews 77: 57-76.

Geissmann, T., 2002b: Taxonomy and evolution of gibbons. In: Anthropology and primatology into the third millennium: The Centenary Congress of the Zürich Anthropological Institute (Evolutionary Anthropology Vol. 11, Supplement 1). Soligo, C.; Anzenberger, G. & Martin, R.D. (eds.), pp. 28-31, New York: Wiley-Liss.

Geissmann, T. & Orgeldinger, M. 1995: Neonatal weight in gibbons (Hylobates spp.). American Journal of Primatology 36: 179-189.

Geissmann, T. & Orgeldinger, M. 2000: The relationship between duet songs and pair bonds in siamangs, Hylobates syndactylus. Animal Behaviour 60: 805-809.

Gittins, S.P. & Raemaekers, J.J. 1980: Siamang, lar and agile gibbons. In Chivers, D.J. (ed.), Malayan forest primates - Ten years' study in tropical rain forest, Plenum Press, New York, pp. 63-105.

Grand, T. I. 1972: A mechanical interpretation of terminal branch feeding. Journal of Mammalogy 53: 198-201.

Larson, S.G. 1988: Subscapularis function in gibbon and chimpanzees: Inplications for interpretation of humeral head torsion in hominoids. American Journal of Physical Anthropology 76: 449-462.

Lovell, Hin-cheung, 1981: Van Gulikís gibbon in China: a dossier of facts and fancies. Orientations vol. 12 issue 11 (November 1981: The Robert Hans van Gulik Issue): pp. 56-61. Hong Kong: Pacific Magazines.

MacKinnon, J. & MacKinnon, K. 1980: Niche differentiation in a primate community. In: Chivers, D.J. (Ed.): Malayan forest primates: Ten years' study in tropical rain forest, pp. 167-190. Plenum Press, New York & London.

Martin, R.D. 1990: Primate origins and evolution. A phylogenetic reconstruction. Chapman and Hall, London.

Miller, C. 1778: Extract from several letters... Giving some account of the interior part of Sumatra. Philosophical Transactions, London 68: 161-179.

Okada, M. 1985: Primate bipedal walking: Comparative kinematics. In: Kondo, S. (Ed.): Primate morphophysiology, locomotor analyses and human bipedalism, pp. 47-58. University of Tokyo, Tokyo.

Palombit, R.A. 1997: Inter- and intraspecific variation in the diets of sympatric siamang (Hylobates syndactylus) and lar gibbons (Hylobates lar). Folia Primatologica 68: 321-337.

Roos, C. & Geissmann, T. 2001: Molecular phylogeny of the major hylobatid divisions. Molecular Phylogenetics and Evolution 19: 486-494.

Schneider, G. 1905: Ergebnisse zoologischer Forschungsreisen auf Sumatra. Erster Teil: Säugetiere (Mammalia). Zoologisches Jahrbuch 23: 1-172, + 3 plates + 2 maps.

Schultz, A.H. 1940: Growth and development of the chimpanzee. Contributions to Embryology 170: 1-63, + 3 plates.

Schultz, A.H. 1941: Growth and development of the orang-utan. Contributions to Embryology 182: 57-110, + 1 plate.

Schultz, A.H. 1944: Age changes and variability in gibbons. A morphological study on a population sample of a man-like ape. American Journal of Physical Anthropology 2(n.s.): 1-129.

Schultz, A.H. 1961: Vertebral column and thorax. In: Hofer, H.; Schultz, A.H. & Starck, D. (Eds.): Primatologia - Handbuch der Primatenkunde, Band 4, Lieferung 5, 66 pp. Karger, Basel and New York.

Schultz, A.H. 1969: The skeleton of the chimpanzee. In: Bourne, G.H. (Ed.): The chimpanzee, vol. 1, p. 50-103. Karger, Basel and New York.

Schultz, A.H. 1972: Die Enzyklopädie der Natur, Band 18: Die Primaten. Éditions Rencontre, Lausanne.

Speidel, G. 1963: Siamang born at Milwaukee County Zoo - First born in captivity. Parks and Recreation 46(1): 56.

van Gulik, R.H. 1967: The gibbon in China. An essay in Chinese animal lore. E. J. Brill, Leiden.

Yamazaki, K. & Ishida, H. 1984: A biomechanical study of vertical climbing and bipedal walking in gibbons. Journal of Human Evolution 13: 563-571.