6Bousfield, W. A. 1953. The Occurrence of clustering in the recall of randomly arranged associates [J]. Journal of General Psychology 49: 229-240.
7Craik, F. I. M. & E. Tulving. 1975. Depth of processing and the retention of words in episodic memory [ J ].Journal of Experimental Psychology 104:268-294.
8Chamot, A. 1984. Identification of ESL learning strategies[P]. Paper Presented at the 18th Annual TESOL Convention. Houston, Texas.
9Richards, J. 1976. The role of vocabulary learning [J].TESOL Quarterly 10: 77-89.