Stewart, William A (1968). "A Sociolinguistic Typology for Describing National Multilingualism". In Fishman, Joshua A (ed.). Readings in the Sociology of Language. The Hague, Paris: Mouton. pp. 531–545. OCLC306499. p. 534.
jstor.org
Kloss, Heinz (1967). "'Abstand languages' and 'ausbau languages'". Anthropological Linguistics. 9 (7): 29–41. JSTOR30029461. p. 31.
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Stewart, William A (1968). "A Sociolinguistic Typology for Describing National Multilingualism". In Fishman, Joshua A (ed.). Readings in the Sociology of Language. The Hague, Paris: Mouton. pp. 531–545. OCLC306499. p. 534.