Pieter Muysken, Introduction: Conceptual and methodological issues in areal linguistics, in Pieter Muysken, „From Linguistic Areas to Areal Linguistics”, 2008 ISBN 90-272-3100-1, p. 30-31 [1]
Lenore A. Grenoble, Language Policy in the Soviet Union, 2003 ISBN 1-4020-1298-5,p. 131 [2]
