http://www.davidpublishing.com/davidpublishing/Upfile/1/22/2013/2013012285889809.PDF
The Effect of Using L1 (Arabic Language) in the L2 (English
Language) Classroom on the Achievement in General English of
Foundation Year Students in King Abdulaziz University
Other research http://www.camtesol.org/Download/LEiA_Vol3_Iss1_2012/LEiA_V3_I1_02_Timor_Use_of_the_Mother_Tongue.pdf
Read Vivian Cook
http://utpjournals.metapress.com/content/5482v66743955633/
http://homepage.ntlworld.com/vivian.c/SLA/UsingL1talk.htm
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Using the First Language in 'the Classroom - Language Resource ...
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Vivian Cook1.