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Pig-tailed langur
Species of Old World monkey

The pig-tailed langur (Simias concolor), a monotypic species in genus Simias, is a large Old World monkey native to islands off Sumatra in Indonesia. This diurnal primate feeds mainly on leaves from the rainforest canopy and lives in single-male, multi-female groups of 3–9 individuals. Two subspecies are recognized: Simias concolor concolor in the southern Mentawai islands, and Simias concolor siberu found only on northern Siberut, which benefits from a protected national park. Populations have declined due to hunting and logging, leading to its critically endangered status by the IUCN.

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Description

The pig-tailed langur is a large and rather heavily built Old World monkey, adapted to climbing with its long arms. Its fur is black-brown, and its hairless face is also black. It is the only monkey in the subfamily Colobinae to have a relatively short tail; the tail is only slightly furred and is only 15 cm (5.9 in) long. The short nose is pointed upward. The pig-tailed langur reaches a full grown length of approximately 50 cm (20 in) and a weight of 7 kg (15 lb).

Sexual dimorphism is exhibited by this species with adult males being larger and heavier than adult females.14 Sexual swelling is exhibited by this species which is rare for single male multi female groups of Colobinae monkeys.15

Classification

Many researchers would like to reclassify this species into the Nasalis genus but phylogenic analyses suggest that these two groups should remain in their separate sister taxa.16 The Critically Endangered status of this primate gives even more reason for it to remain under the genus Simias since the grouping of these genera could affect conservation efforts.17

Diet

It is an omnivore with a diet consisting of leaves, flowers, fruits and occasionally insects. The availability of these foods in this area are abundant especially in unripe and ripe fruits.18 Leaves are the most abundant in their diet followed by fruits.19  As with all other Colobinae primates, this species is diurnal.

Distribution and social systems

This primate is endemic to the Mentawai Islands, there are two subspecies, Simias concolor concolor also known as simasepsep which resides on the southern islands of Sipora, North Pagai, and South Pagai.20 The second subspecies is Simias concolor siberut also known as simakobou which lives only on the island of Siberut.21 It is a diurnal and arboreal rain forest dweller, often spending most of its time in the canopy but occasionally comes to ground.22 The activity budget of this primate is mostly resting and feeding with a small fraction of time devoted towards travel and social behavior.23 Some studies in the Siberut area show relatively low group sizes (mean group size 2.6).24 Other parts in Siberut show relatively high group sizes (mean group size 8.7).25 The reason for different group sizes is not factually known, however many researchers suggest that it could be due to anthropogenic factors such as hunting and deforestation.26 The pig-tailed langur has single-male, multi-female groups. The mating system of this species follows a polygynous structure although it was originally thought to be monogamous.27

Endangerment status and threats to conservation

This species is classified as Critically endangered by the International Union for Conservation of Nature.28 It was classified as Endangered (IUCN status) up until 2008 were the endangerment status was changed to Critically Endangered.29 It is among The World's 25 Most Endangered Primates due to the many anthropogenic pressures it faces on the islands30 which include, destruction of forest for commercial use, hunting and illegal pet trade.31 Population size estimates have been conducted across many years with varying islands being chosen for research areas. In the 1980s population estimates of the Pig-tailed langur was 19,000 on the island of Siberut and 26,000 across all four islands.32 In 2004 Lisa M. Paciulli dedicated their PhD dissertation towards studying threats to Mentawai island primates and determining population densities associated with logging pressures.33 Population estimates were found to be around 6,700-17,300 across all islands with a large amount of variation being attributed due to hunting and logging pressures.34 Population densities were 2.5 individuals/km2 in logged areas whereas unlogged areas had a population density of 5 individuals/km2.35

An extensive population density survey was conducted by the University of Indonesia on four endemic Mentawai primates. This research was exclusive to the southern Mentawai islands and included a variety of survey areas, most of which devastated by commercial logging. The results of the 2008–2009 surveys are population densities of 1.5 groups/km2 on the island of Sipora and 2.1 ± 0.3 groups/km2 on the Pagai islands with group sizes around 3 individuals.36 Research into population densities on the northern Mentawai island of Siberut is more abundant due to the lower mean population densities of humans living on this island as well as the considerable amount of forestry that remains in comparison to the southern Mentawai islands. In northern Siberut researchers in the Peleonan forest conducted population density surveys from July to December 2005.37  Results form these surveys show a mean density of 16.2 groups/km2.38

One of the main factors associated with the population decline of this species is habitat disturbance from commercial logging operations.39 Forestry cover varies significantly among the islands. The island of Siberut has most of its area declared as a National park whereas the southern islands of Sipora, North Pagai, and South Pagai have limited areas of forestry conservation.40 It is estimated that Siberut's forest cover decreased from 3,500 km2 to 2,400 km2 and the southern Mentawai islands of Sipora and Pagai have decreased from 1300 km2 to 300 km2.41 The reason for Siberut's extensive forestry cover in comparison to the southern islands is due to historical conservation efforts. Much of the efforts started in the 1980s with the help of UNESCO man and the Biosphere reserve.42 This was expanded in the 1990s were a large portion of Siberut was declared a National Park.43 The declaration of this National Park allowed for hunting and logging operations to be significantly reduced; although areas around the national park still experience pressures of logging and conversions to commercial palm oil plantations through concessions and illegal activities.44 Many of the areas in the southern Mentawai islands have experienced heavy logging operations that have left little forestry for the Mentawai primates. Most of the forestry has now been reduced from primary forestry to secondary forestry which is troubling since the pig-tailed langur thrives in arboreal environments.45

The reduction on forestry in the southern Mentawai islands creates a domino effect of paving new land for more human activities and settlement.46 The second main factor associated with the population decline of this species is hunting. Local inhabitants have historically used arrows and poisonous materials to hunt this species.47 However technological advancements of firearms have facilitated the hunting of this species, especially since it is one of the largest primates on these islands.48 Many local inhabitants hunt this species because it is considered a delicacy, with many locals saying it has the best tasting meat compared to other primates.4950 Population density data suggests that an increase in hunting pressure at survey sites results in lower population densities of this primate.51

Subspecies

  • Genus Simias 52
    • Pig-tailed langur, Simias concolor
      • Simias concolor concolor
      • Simias concolor siberu

References

  1. Quinten, M.; Setiawan, A.; Cheyne, S.; Traeholt, C.; Whittaker, D. (2020). "Simias concolor". IUCN Red List of Threatened Species. 2020: e.T20229A17953422. doi:10.2305/IUCN.UK.2020-2.RLTS.T20229A17953422.en. Retrieved 19 November 2021. https://www.iucnredlist.org/species/20229/17953422 ↩

  2. Schwitzer, C., Mittermeier, R.A., Rylands, A.B., Chiozza, F., Williamson, E.A., Byler, D., Wich, S., Humle, T., Johnson, C., Mynott, H., and McCabe, G. (eds.). 2019. Primates in Peril: The World’s 25 Most Endangered Primates 2018–2020. IUCN SSC Primate Specialist Group, International Primatological Society, Global Wildlife Conservation, and Bristol Zoological Society, Washington, DC. 57–58pp ↩

  3. Hadi, Susilo; Ziegler, Thomas; Waltert, Matthias; Syamsuri, Fauzan; Mühlenberg, Michael; Hodges, J. Keith (2012). "Habitat Use and Trophic Niche Overlap of Two Sympatric Colobines, Presbytis potenziani and Simias concolor, on Siberut Island, Indonesia". International Journal of Primatology. 33 (1): 218–232. doi:10.1007/s10764-011-9567-y. ISSN 0164-0291. S2CID 11087889. http://link.springer.com/10.1007/s10764-011-9567-y ↩

  4. Waltert, Matthias; Abegg, Christophe; Ziegler, Thomas; Hadi, Susilo; Priata, Dodi; Hodges, Keith (2008). "Abundance and community structure of Mentawai primates in the Peleonan forest, north Siberut, Indonesia". Oryx. 42 (3): 375–379. doi:10.1017/S0030605308000793 (inactive 11 March 2025). ISSN 1365-3008. S2CID 208530127.{{cite journal}}: CS1 maint: DOI inactive as of March 2025 (link) /wiki/Doi_(identifier) ↩

  5. Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml ↩

  6. Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203. ↩

  7. Tenaza, Richard R. (1989). "Female sexual swellings in the Asian colobine Simias concolor". American Journal of Primatology. 17 (1): 81–86. doi:10.1002/ajp.1350170108. ISSN 0275-2565. PMID 31968853. S2CID 83904665. https://onlinelibrary.wiley.com/doi/10.1002/ajp.1350170108 ↩

  8. Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml ↩

  9. Paciulli, L. M. (2004). The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates (PhD thesis). State University of New York, Stony Brook. ↩

  10. Whittaker, Danielle J.; Ting, Nelson; Melnick, Don J. (2006-06-01). "Molecular phylogenetic affinities of the simakobu monkey (Simias concolor)". Molecular Phylogenetics and Evolution. 39 (3): 887–892. Bibcode:2006MolPE..39..887W. doi:10.1016/j.ympev.2005.12.013. ISSN 1055-7903. PMID 16516500. https://www.sciencedirect.com/science/article/pii/S105579030500429X ↩

  11. Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203. ↩

  12. Lanjouw, Annette (2021). "De-colonizing conservation in a global world". American Journal of Primatology. 83 (4): e23258. doi:10.1002/ajp.23258. ISSN 0275-2565. PMC 8244066. PMID 33764605. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8244066 ↩

  13. Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203. ↩

  14. Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml ↩

  15. Tenaza, Richard R. (1989). "Female sexual swellings in the Asian colobine Simias concolor". American Journal of Primatology. 17 (1): 81–86. doi:10.1002/ajp.1350170108. ISSN 0275-2565. PMID 31968853. S2CID 83904665. https://onlinelibrary.wiley.com/doi/10.1002/ajp.1350170108 ↩

  16. Whittaker, Danielle J.; Ting, Nelson; Melnick, Don J. (2006-06-01). "Molecular phylogenetic affinities of the simakobu monkey (Simias concolor)". Molecular Phylogenetics and Evolution. 39 (3): 887–892. Bibcode:2006MolPE..39..887W. doi:10.1016/j.ympev.2005.12.013. ISSN 1055-7903. PMID 16516500. https://www.sciencedirect.com/science/article/pii/S105579030500429X ↩

  17. Whittaker, Danielle J.; Ting, Nelson; Melnick, Don J. (2006-06-01). "Molecular phylogenetic affinities of the simakobu monkey (Simias concolor)". Molecular Phylogenetics and Evolution. 39 (3): 887–892. Bibcode:2006MolPE..39..887W. doi:10.1016/j.ympev.2005.12.013. ISSN 1055-7903. PMID 16516500. https://www.sciencedirect.com/science/article/pii/S105579030500429X ↩

  18. Erb, Wendy M.; Borries, Carola; Lestari, Nurul S.; Hodges, J. Keith (2012-12-01). "Annual Variation in Ecology and Reproduction of Wild Simakobu (Simias concolor)". International Journal of Primatology. 33 (6): 1406–1419. doi:10.1007/s10764-012-9630-3. ISSN 1573-8604. S2CID 14982894. https://doi.org/10.1007/s10764-012-9630-3 ↩

  19. Erb, Wendy M.; Borries, Carola; Lestari, Nurul S.; Hodges, J. Keith (2012-12-01). "Annual Variation in Ecology and Reproduction of Wild Simakobu (Simias concolor)". International Journal of Primatology. 33 (6): 1406–1419. doi:10.1007/s10764-012-9630-3. ISSN 1573-8604. S2CID 14982894. https://doi.org/10.1007/s10764-012-9630-3 ↩

  20. Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203. ↩

  21. Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203. ↩

  22. Hadi, Susilo; Ziegler, Thomas; Waltert, Matthias; Syamsuri, Fauzan; Mühlenberg, Michael; Hodges, J. Keith (2012). "Habitat Use and Trophic Niche Overlap of Two Sympatric Colobines, Presbytis potenziani and Simias concolor, on Siberut Island, Indonesia". International Journal of Primatology. 33 (1): 218–232. doi:10.1007/s10764-011-9567-y. ISSN 0164-0291. S2CID 11087889. http://link.springer.com/10.1007/s10764-011-9567-y ↩

  23. Hadi, Susilo; Ziegler, Thomas; Waltert, Matthias; Syamsuri, Fauzan; Mühlenberg, Michael; Hodges, J. Keith (2012). "Habitat Use and Trophic Niche Overlap of Two Sympatric Colobines, Presbytis potenziani and Simias concolor, on Siberut Island, Indonesia". International Journal of Primatology. 33 (1): 218–232. doi:10.1007/s10764-011-9567-y. ISSN 0164-0291. S2CID 11087889. http://link.springer.com/10.1007/s10764-011-9567-y ↩

  24. Waltert, Matthias; Abegg, Christophe; Ziegler, Thomas; Hadi, Susilo; Priata, Dodi; Hodges, Keith (2008). "Abundance and community structure of Mentawai primates in the Peleonan forest, north Siberut, Indonesia". Oryx. 42 (3): 375–379. doi:10.1017/S0030605308000793 (inactive 11 March 2025). ISSN 1365-3008. S2CID 208530127.{{cite journal}}: CS1 maint: DOI inactive as of March 2025 (link) /wiki/Doi_(identifier) ↩

  25. Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml ↩

  26. Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml ↩

  27. Hadi, Susilo; Ziegler, Thomas; Hodges, J. Keith (2009-02-08). "Group Structure and Physical Characteristics of Simakobu Monkeys (Simias concolor) on the Mentawai Island of Siberut, Indonesia". Folia Primatologica. 80 (2): 74–82. doi:10.1159/000214226. ISSN 1421-9980. PMID 19390200. S2CID 2480140. https://brill.com/view/journals/ijfp/80/2/article-p74_3.xml ↩

  28. Quinten, M.; Setiawan, A.; Cheyne, S.; Traeholt, C.; Whittaker, D. (2020). "Simias concolor". IUCN Red List of Threatened Species. 2020: e.T20229A17953422. doi:10.2305/IUCN.UK.2020-2.RLTS.T20229A17953422.en. Retrieved 19 November 2021. https://www.iucnredlist.org/species/20229/17953422 ↩

  29. Quinten, M.; Setiawan, A.; Cheyne, S.; Traeholt, C.; Whittaker, D. (2020). "Simias concolor". IUCN Red List of Threatened Species. 2020: e.T20229A17953422. doi:10.2305/IUCN.UK.2020-2.RLTS.T20229A17953422.en. Retrieved 19 November 2021. https://www.iucnredlist.org/species/20229/17953422 ↩

  30. Schwitzer, C., Mittermeier, R.A., Rylands, A.B., Chiozza, F., Williamson, E.A., Byler, D., Wich, S., Humle, T., Johnson, C., Mynott, H., and McCabe, G. (eds.). 2019. Primates in Peril: The World’s 25 Most Endangered Primates 2018–2020. IUCN SSC Primate Specialist Group, International Primatological Society, Global Wildlife Conservation, and Bristol Zoological Society, Washington, DC. 57–58pp ↩

  31. Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203. ↩

  32. Whittaker, Danielle J. (2006). "A Conservation Action Plan for the Mentawai Primates". Primate Conservation. 2006 (20): 95–105. doi:10.1896/0898-6207.20.1.95. ISSN 0898-6207. S2CID 85765480. https://bioone.org/journals/primate-conservation/volume-2006/issue-20/0898-6207.20.1.95/A-Conservation-Action-Plan-for-the-Mentawai-Primates/10.1896/0898-6207.20.1.95.full ↩

  33. Paciulli, L. M. (2004). The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates (PhD thesis). State University of New York, Stony Brook. ↩

  34. Paciulli, L. M. (2004). The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates (PhD thesis). State University of New York, Stony Brook. ↩

  35. Paciulli, L. M. (2004). The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates (PhD thesis). State University of New York, Stony Brook. ↩

  36. Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203. ↩

  37. Waltert, Matthias; Abegg, Christophe; Ziegler, Thomas; Hadi, Susilo; Priata, Dodi; Hodges, Keith (2008). "Abundance and community structure of Mentawai primates in the Peleonan forest, north Siberut, Indonesia". Oryx. 42 (3): 375–379. doi:10.1017/S0030605308000793 (inactive 11 March 2025). ISSN 1365-3008. S2CID 208530127.{{cite journal}}: CS1 maint: DOI inactive as of March 2025 (link) /wiki/Doi_(identifier) ↩

  38. Waltert, Matthias; Abegg, Christophe; Ziegler, Thomas; Hadi, Susilo; Priata, Dodi; Hodges, Keith (2008). "Abundance and community structure of Mentawai primates in the Peleonan forest, north Siberut, Indonesia". Oryx. 42 (3): 375–379. doi:10.1017/S0030605308000793 (inactive 11 March 2025). ISSN 1365-3008. S2CID 208530127.{{cite journal}}: CS1 maint: DOI inactive as of March 2025 (link) /wiki/Doi_(identifier) ↩

  39. Paciulli, L. M. (2004). The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates (PhD thesis). State University of New York, Stony Brook. ↩

  40. Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203. ↩

  41. Whittaker, Danielle J. (2006). "A Conservation Action Plan for the Mentawai Primates". Primate Conservation. 2006 (20): 95–105. doi:10.1896/0898-6207.20.1.95. ISSN 0898-6207. S2CID 85765480. https://bioone.org/journals/primate-conservation/volume-2006/issue-20/0898-6207.20.1.95/A-Conservation-Action-Plan-for-the-Mentawai-Primates/10.1896/0898-6207.20.1.95.full ↩

  42. Whittaker, Danielle J. (2006). "A Conservation Action Plan for the Mentawai Primates". Primate Conservation. 2006 (20): 95–105. doi:10.1896/0898-6207.20.1.95. ISSN 0898-6207. S2CID 85765480. https://bioone.org/journals/primate-conservation/volume-2006/issue-20/0898-6207.20.1.95/A-Conservation-Action-Plan-for-the-Mentawai-Primates/10.1896/0898-6207.20.1.95.full ↩

  43. Whittaker, Danielle J. (2006). "A Conservation Action Plan for the Mentawai Primates". Primate Conservation. 2006 (20): 95–105. doi:10.1896/0898-6207.20.1.95. ISSN 0898-6207. S2CID 85765480. https://bioone.org/journals/primate-conservation/volume-2006/issue-20/0898-6207.20.1.95/A-Conservation-Action-Plan-for-the-Mentawai-Primates/10.1896/0898-6207.20.1.95.full ↩

  44. Whittaker, Danielle J. (2006). "A Conservation Action Plan for the Mentawai Primates". Primate Conservation. 2006 (20): 95–105. doi:10.1896/0898-6207.20.1.95. ISSN 0898-6207. S2CID 85765480. https://bioone.org/journals/primate-conservation/volume-2006/issue-20/0898-6207.20.1.95/A-Conservation-Action-Plan-for-the-Mentawai-Primates/10.1896/0898-6207.20.1.95.full ↩

  45. Yanuar, A.; Supriatna, J. (2018). "The Status of Primates in the Southern Mentawai Islands, Indonesia". Primate Conservation. 32: 193–203. ↩

  46. Lanjouw, Annette (2021). "De-colonizing conservation in a global world". American Journal of Primatology. 83 (4): e23258. doi:10.1002/ajp.23258. ISSN 0275-2565. PMC 8244066. PMID 33764605. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8244066 ↩

  47. Paciulli, L. M. (2004). The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates (PhD thesis). State University of New York, Stony Brook. ↩

  48. Paciulli, L. M. (2004). The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates (PhD thesis). State University of New York, Stony Brook. ↩

  49. Schwitzer, C., Mittermeier, R.A., Rylands, A.B., Chiozza, F., Williamson, E.A., Byler, D., Wich, S., Humle, T., Johnson, C., Mynott, H., and McCabe, G. (eds.). 2019. Primates in Peril: The World’s 25 Most Endangered Primates 2018–2020. IUCN SSC Primate Specialist Group, International Primatological Society, Global Wildlife Conservation, and Bristol Zoological Society, Washington, DC. 57–58pp ↩

  50. Paciulli, L. M. (2004). The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates (PhD thesis). State University of New York, Stony Brook. ↩

  51. Paciulli, L. M. (2004). The effects of logging, hunting, and vegetation on the densities of the Pagai, Mentawai Islands primates (PhD thesis). State University of New York, Stony Brook. ↩

  52. Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press. p. 175. ISBN 0-801-88221-4. OCLC 62265494. 0-801-88221-4 ↩