1. Dpealcio, Fact Sheet 2009, The Service Sector:Projections and Current Stats, http://dpeaflcio.org/programs/factsheets/fs_2009_service_sector.pdf
2. L. Roberts, Applying SPC in a Service Environment, (Roberts & Roberts Associates, Plano, TX, 1995).
3. D. T. Seymour, On Q: Causing Quality in Higher Education. (Mcmillan Publishing Company, NY,1992).
4. B. H. Yeap, “A new perspectives for quality improvement in teaching and learning processes” in Sustainability in Higher Education: Directions for Change-2008, edited by J. Renner, J. Cross, & L. McCormack, Proceeding of the 4th International Conference (EDU-COM 2008), (Edith Cowan University,Jondaloop, WA Australia, 2008), pp. 583–590.
5. Children's Learning Difficulties: A Cognitive Approach