2 Lowie WM. The acquisition of interlanguage morphology: A study into the role of morphology in the L2 learner’s mental lexicon. Groningen: University of Groningen 1998;
3 Wedrana, Mihalicek et al..Language files, Material for an introduction to Language and Linguistics. Eleventh Edition. The Ohio State University Press.2011.-P.89.
4 Malmkjaer, Kirsten. 2002. The Linguistics Encyclopedia: 2nd edition. London and New York: Routledge.
5 Agus mortoyo et al 2012. Actual Bahasa Inggris. Gema Aksara Mnahan Solo.