Stern, H. H. Fundamental Concepts of Language Teaching: Historical and Interdisciplinary Perspectives on Applied Linguistic Research. اوکسفرڈ یونیورسٹی پریس. 24 March 1983. p. 55. Retrieved from Google Books on اکتوبر 17, 2012. ISBN0194370658, 9780194370653.
Decoo, Wilfried. Systemization in Language Learning Models. Taylor & Francis US , جنوری 1, 2009. p. 63. Retrieved from گوگل بکس on 17 اکتوبر 2012. ISBN0415361931, 9780415361934
