also been done among users of sign languages (Vasishta, Woodward, and Wilson 1978, Woodward 1991, 1993, 1996, Parkhurst & Parkhurst 1998, Al-Fityani & Padden 2008). As with surveys among spoken languages, surveys among sign languages have studied multilingualism, attitudes about various languages both spoken and signed (Ciupek-Reed 2012), differences and similarities between signed varieties (Aldersson and McEntee-Atalianis 2007, Bickford 1991, 2005, Parks 2011), and assessing the vitality of signed languages, and initial descriptions of undocumented sign languages. Adopting and adapting the concept of "extensibility" from spoken languages, Jason Hopkins wrote about how this could be applied to surveying sign languages. References References: sample survey reports Acharya, A. S. 1976. Tiptur Kannada. Linguistic Survey of India Series, no. 8. Poona: Deccan College Postgraduate and Research Institute. Aldersson, Russell R. and Lisa J. McEntee-Atalianis. 2007. A Lexical Comparison of Icelandic Sign Language and Danish Sign Language. Birkbeck Studies in Applied Linguistics 2 Icelandic & Danish Sign Languages Al-Fityani, Kinda & Carole Padden. 2008. A lexical comparison of sign languages in the Arab world. In R. M. de Quadros (Ed.), Sign languages: Spinning and unraveling the past, present, and future. TISLR9, forty five papers and three posters from the 9th Theoretical Issues in Sign Language Research Conference. Florianopolis, Brazil, December 2006. Petrópolis, RJ, Brazil: Editora Arara Azul. Downloadable Backstrom, Peter C. 1992. "Wakhi." In Peter C. Backstrom and Carla J. Radloff (eds.), Languages of northern areas, 57-74. Sociolinguistic Survey of Northern Pakistan, 2. Islamabad: National Institute of Pakistan Studies, Quaid-i-Azam University and Summer Institute of Linguistics. Bender, M. L. 1971. The languages of Ethiopia. A new lexicostatistic classification and some problems of diffusion. Anthropological Linguistics 13(5): 165-288. Bender, M. L., J. D. Bowen, R. L. Cooper, and C. A. Ferguson. 1976. Language in Ethiopia. London: Oxford University Press. Beyer, Daniela and Simone Beck. 2011. A Linguistic Assessment of the Munji language in Afghanistan. Language Documentation and Conservation 6: 38-103. Bickford, J. Albert. 1991. Lexical variation in Mexican Sign Language. Sign Language Studies 72:241–276. Bickford, J. Albert. 2005. The signed languages of Eastern Europe. SIL Electronic Survey Reports 2005-026: 45. http://www.sil.org/silesr/abstract.asp?ref=2005-026 Clifton, John M., editor. 2002. Studies in languages of Azerbaijan, vol. 1,2. Baku, Azerbaijan and St. Petersburg, Russia: Institute of International Relations, Academy of Sciences of Azerbaijan and North Eurasian Group, SIL International. Clifton, John M., editor. 2005. Studies in languages of Tajikistan. Dushanbe, Tajikistan: National State University of Tajikistan; St. Petersburg, Russia