BIBLIOGRAPHY:

Oxford Advanced Learner's Dictionary of Current
English,Oxford
University Press
Raymond Murphy: English Grammar in Use, Cambridge
University Press
Martin Hewings: Advanced Grammar in Use, Cambridge
University Press
G. Leech and J. Svartvik: A Communicative Grammar of
English, Longman
Longman Interactive English Dictionary, First Edition,
1993, Longman
Group UK Limited
http://esl.about.com/