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The 1991 census recognizes 1,576 classified "mother tongues". According to the 1991 census, 22 languages had more than a million native speakers, 50 had more than 100,000 and 114 had more than 10,000 native speakers. The remaining accounted for a total of 566,000 native speakers (out of a total of 838 million Indians in 1991).
The number of Sanskrit speakers in India in 1991 census was 49,736.
Jammu and Kashmir was excluded from census-taking in 1991 due to Insurgency in Jammu and Kashmir. The number for J&K was derived by interpolation for the population of religious communities in the state.
Census was not conducted in Assam in the previous census in 1981 due to separatist movements that time. The census data for Assam was done based on interpolation.
^ Vijayanunni, M. (26–29 August 1998). "Planning for the 2001 Census of India based on the 1991 Census" (PDF). 18th Population Census Conference. Honolulu, Hawaii, US: Association of National Census and Statistics Directors of America, Asia, and the Pacific. Archived from the original (PDF) on 19 November 2008. Retrieved 17 December 2014.
Dev, Amiya (2010). "Literary Multilingualism II : Multilingualism in India". In Lisa Block de Behar; Paola Mildonian; Jean-Michel Djian; Djlel Kadir; Alfons Knauth; Dolores Romero Lopez; Marcio Orlando Seligmann-Silva (eds.). Comparative Literature : Sharing Knowledges for Preserving Cultural Diversity (PDF). Encyclopedia of Life Support Systems. Vol. 2. pp. 172–183. Developed under the Auspices of the UNESCO, EOLSS Publishers, Paris, France, . Retrieved 17 December 2014.