Creswell, J.W. (2000). Research Design: Qualitative, Quantitative, and Mixed Methods Approaches (2nd ed.). Thousand Oaks , CA : Sage Publications.

Frechtling, J., & Sharp, L. (1997). User-Friendly Handbook for Mixed Method Evaluations . Arlington , VA : National Science Foundation.

Miles, M.B., & Huberman, A.M. (1994). Qualitative Data Analysis (2nd ed.). Newbury Park , CA : Sage Publications.

Tyler, R. (1990). Reporting evaluations of learning outcomes. In H. J. Walberg & G. D. Haertel (Eds.), The International Encyclopedia of Educational Evaluation (pp. 733-738). Oxford , England : Pergamon.

Yin, R.K. (1998). The abridged version of case study research: Design and method. In L. Bickman & D. J. Rog (Eds.), Handbook of Applied Social Research Methods (pp. 229-260). Thousand Oaks , CA : Sage Publications.