Acknowledgement
I would like to express my deep and sincere gratitude to my honorable professor and thesis supervisor, Dr. Rezaee, for his invaluable and constructive comments, and for his vital support throughout this work. His understanding, encouraging and personal guidance have provided a good basis for the present thesis. Without his well-designed plan and meticulous review of the draft, this research would have been impossible. Thank you Sir. Your many helpful comments were worth gold.
I am grateful to my thesis reader, Dr. Alavi, for his valuable advice and friendly help. His kind support and guidance have been of great value in this study. Thank you doesn’t seem sufficient but it is said with appreciation and respect.
My sincere thanks are due to the official referee, Dr. Borzabadi, for his detailed review, constructive criticism and excellent advice.
My special appreciation goes to all my dedicated professors at the University of Tehran whose priceless and indubitable efforts throughout these years was a constant source of encouragement and confidence to me and my classmates. I feel privileged to have been able to work with them.
I would also like to extend my warmest thanks to all those who have helped me with my work, especially to the students who kindly agreed to participate in this research as well as to their respectable teachers who gave their permission to conduct this research in their classrooms.
I cannot end without thanking my adorable parents, on whose constant encouragement and love I have relied throughout my time studying in the university. Without their encouragement and understanding it would have been impossible for me to finish this work. My special gratitude is due to my brothers, my sister and their families for their loving support.
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