Akaike H (1973) Information theory and an extension of the maximum likelihood principle. In: Petrv BN, Csaki F (eds) Proceedings of the 2nd international symposium on information theory. Akademiai Kiado, Budapest, pp 267–281
Andriolo A, Piovezan U, da Costa MJRP, Laake J, Duarte JMB (2005) Aerial line transect survey to estimate abundance of marsh deer (Blastocerus dichotomus) (Illiger, 1815). Brazilian Arch Biol Technol 48:807–814
Barnes RFW, Dunn A (2002) Estimating forest elephant density in Sapo National Park (Liberia) with a rainfall model. Afr J Ecol 40:159–163
Boitani L, Fuller TK (2000) Research techniques in animal ecology: controversies and consequences. Columbia University Press, New York
Bookhout TA (1996) Research and management techniques for wildlife and habitats. Allen Press, Lawrence, Kansas
Buckland ST, Anderson DR, Burnham KP, Laake JL (1993) Distance sampling: estimating abundance of biological populations. Chapman & Hall, London
Buckland ST, Anderson DR, Burnham KP, Laake JL, Borchers DL, Thomas L (2001) Introduction to distance sampling: estimating abundance of biological populations. Oxford University Press, New York
Buechner HK (1960) The bighorn sheep in the United States, its past, present, and future. Wlidl Monogr 4:1–173
Cao LR, Liu ZS, Wang XM, Hu TH, Li T, Zhai H, Hou JH (2005a) Preliminary study on group characteristics of blue sheep (Pseudois nayaur) in spring and early winter in Helan Mountains, China. Chin J Zool 40:28–33
Cao LR, Liu ZS, Wang XM, Hu TH, Zhai H, Hou JH (2005b) Winter group size and composition of blue sheep (Pseudois nayaur) in the Helan Mountains, China. Acta Theriol Sinica 25:200–204
Di VZ (1986) Plantae vasculares Helan Mountain. Northwestern University Press, Xi'an
Focardi S, Montanaro P, Isotti R, Ronchi M, Scacco M, Calmanti R (2005) Distance sampling effectively monitored a declining population of Italian roe deer Capreolus capreolus italicus. Oryx 39:1–8
Fox JL, Bårdsen B-J (2005) Density of Tibetan antelope, Tibetan wild ass and Tibetan gazelle in relation to human presence across the Chang Tang Nature Reserve of Tibet, China. Acta Zool Sinica 51:586–597
Gusset M, Burgener N (2005) Estimating large carnivore numbers from track counts and measurements. Afr J Ecol 43:320–324
Harris RB, Burnham KP (2002) On estimating wildlife densities from line transect data. Acta Zool Sinica 48:812–818
Harris RB, Ali A, Loggers C (2005) Trend monitoring of large mammals: two case studies. Acta Theriol Sinica 25:319–325
Hiby L, Krishna MB (2001) Line transect sampling from a curving path. Biometrics 57:727–731
Hounsome TD, Yong RP, Davison J, Yarnell RW, Trewby ID, Garnet BT, Delahay RJ, Wilson GJ (2005) An evaluation of distance sampling to estimate badger (Meles meles) abundance. J Zool Lond 266:81–87
Hyrenbach KD, Baduini C L, Hunt JR G L (2001) Line transect estimates of short-tailed shearwater Puffinus tenuirostris mortality in the south-eastern Bering Sea, 1997–1999. Mar Ornithol 29:11–18
International Union for the Conservation of Nature and Natural Resources (IUCN) (2006) 2006 IUCN Red List of threatened species. http://www.iucnredlist.org
Jachmann H (2002) Comparison of aerial counts with ground counts for large African herbivores. J Appl Ecol 39:841–852
Li Y C, Koganezawa M (2004) A density estimate of sika deer using distance sampling techniques in forested habitat. Acta Zool Sinica 50:27–31
Liu ZX, Sheng HL, Li YG, Wang ZD, Zhao DH, Du HP (2000) The current status and conservation of isolated population of alpine musk deer (Moschus chrysogaster) at Helan Mountain. Acta Ecol Sin 20:463–467
Liu ZS, Cao LR, Wang XM, Li T, Li ZG (2005a) Winter bed-site selection by blue sheep (Pseudois nayaur) in Helan Mountain, Ningxia, China. Acta Theriol Sinica 25:1–8
Liu ZS, Wang XM, Li ZG, Cui DY, Li XQ (2005b) Comparison of feeding habitat by blue sheep (Pseudois nayaur) during winter and spring in Helan Mountain, China. Zool Res 26:580–589
Liu ZS, Wang XM, Li ZG, Cui DY, Li XQ (2005c) Diurnal activity rhythm of blue sheep (Pseudois nayaur) in Helan Mountain: variation of season, age and sex. Zool Res 26:350–357
Lü HJ, Li ZG, Zhai H, Li T, Hu TH, Zhao CJ (2000) Monitoring and survey of blue sheep in Germany-aided project area of state natural reserve of Helanshan Mountain in Ningxia. Ningxia J Agric Forestry 15–18
Marques FFC, Buckland ST, Goffin D, Dixon CE, Borchers DL, Mayle BA, Peace AJ (2001) Estimating deer abundance from line transect surveys of dung: sika deer in southern Scotland. J Appl Ecol 38:349–363
Mishra C, Van Wieren SE, Ketner P, Heitkönig IMA, Prins HHT (2004) Competition between domestic livestock and wild bharal Pseudois nayaur in the Indian Trans-Himalaya. J Appl Ecol 41:344–354
Newey S, Bell M, Enthoven S, Thirgood S (2003) Can distance sampling and dung plots be used to assess the density of mountain hares Lepus timidus? Wildlife Biol 9:185–192
Olson KA, Fuler TK, Schaller GB, Odonkhuu D, Murray MG (2005) Estimating the population density of Mongolian gazelles Procapra gutturosa by driving long-distance transects. Oryx 39:164–169
Plumptre AJ (2000) Monitoring mammal populations with line transect techniques in African forests. J Appl Ecol 37:356–368
Ren QF, Guo HL, Li ZG, Dai JX (1999) The quantity and resources exploitation of blue sheep in Ningxia. Ningxia J Agric Forestry, 38–42
Schaller GB (1998) Wildlife of the Tibetan Steppe. University of Chicago Press, Chicago
Schaller GB, Li H, Talipu, Lu H, Ren J, Qiu M, Wang H (1987) Status of large mammals in Taxtorgan Reserve, Xinjiang, China. Biol Conserv 42:53–71
Shackleton DM (ed) and the IUCN/SSC Caprinae Specialist Group (1997) Wild sheep and goats and their relatives. Status survey and conservation action plan for Caprinae. IUCN, Gland, Switzerland and Cambridge, UK
Smart JCR, Ward AI White PCL (2004) Monitoring woodland deer population in the UK: an imprecise science. Mammal Rev 34:99–114
Thomas L, Laake JL, Strindberg S, Marques FFC, Buckland ST, Borchers DL, Anderson DR, Burnham KP, Hedley SL, Pollard JH, Bishop JRB, Marques TA (2005) Distance 5.0. Release 1. Research Unit for Wildlife Population Assessment, University of St Andrews, UK. http://www.ruwpa.st-and.ac.uk/distance/
Wang XM, Schaller GB (1996) Status of large mammals in Inner Mongolia, China. J East China Norm Univ (Special issue of Mammals) 6:94–104
Wang XM, Li M, Tang SY, Liu ZX (1998a) A preliminary study of some characters of blue sheep population ecology in spring. Acta Theriol Sinica 18:27–33
Wang XM, Liu ZX, Xu HF, Li M, Li YG (1998b) The blue sheep population ecology and its conservation in Helan Mountain, China. Chin Biodivers 6:1–5
Wang XM, Liu ZS, Li XQ, Li ZG (2005) Comparison of age structure of male blue sheep (Pseudois nayaur) on Helan Mountains in two periods, 1995 and 2004. Zool Res 26:467–472
Wang XM, Cao LR, Liu ZS, Fang SG (2006) Mitochondrial DNA variation and matrilineal structure in blue sheep populations of Helan Mountain, China. Can J Zool 84:1431–1439
Ward AI, White PCL, Critchley CH (2004) Roe deer Capreolus capreolus behaviour affects estimates from distance sampling surveys. Mammal Rev 34:315–319
Wegge P (1979) Aspects of population ecology of blue sheep in Nepal. J Asian Ecol 1:10–20
Yost AC, Wright RG (2001) Moose, caribou, and grizzly bear distribution in relation to road traffic in Denali National Park, Alaska. Arctic 54:41–48
Yu YQ, Guo ST, Bai QS, Li ZG, Hu TH, Lü HJ (2004) The seasonal change of blue sheep population structure in Helanshan Mountains. Acta Theriol Sinica 24:200–204