Acknowledgement
I would like to express my deepest gratefulness to my lecturer, Dr. Nurul Ain Mohd Tahir for her patience, guidance and assistance throughout the study. I would also like to thank Professor Shu Chuen Li for always being willing to help and give excellent ideas for improvement. Lastly, I would also like to show my appreciation to my teammate, Geok Ying for helping me through the process of conducting a systematic review.