Ahmad Md Sharif (1994)Effandi Zakaria (1998)Hamm dan Adams (1994)Johnson & Johnson (1987)Johnson dan Johnson (1985)Johnson, Johnson dan Smith (1991)Linda Tiong Ming (2004)Muhammad Hazman (2009). Teknik Pengumpulan Data Kajian Tindakan, Miles & Huberman (1994)Shellet Anand (2002)Sabihta (2009)Wan Nur Azyyati (2007)