1. Abdulahi, F. (2006). Measuring service quality in higher education HEDPERF and SERVPERF. Marketing Intelligence and Planning 24(1): 31–47.
2. Accenture. (2013). Huge cost profile makes Nigerian airlines high-risk business. Business Day Newspaper. Retrieved: June 2014, from: http://www.businessdaynewspaper/huge-cost-profile-makes-nigerian-airlines-high-risk-business.
3. Airport Cooperative Research Program (2013). How airports measure customer service performance: A synthesis of airport practice. Research sponsored by the Federal Aviation Administration, Transportation Research Board, Washington, D. C. Retrieved: September 7, 2014, from: http://www.TRB.org.
4. Aldridge, S.; Rowley, J. (1998). Measuring customer satisfaction in higher education. Quality Assurance in Education 6(4): 197–204.
5. Amin, M. E. (2005). Social science research: Conception, methodology and analysis. Kampala: Makerere University Press.