(11.1) Kim D. Reynolds and Stephen G. West. A Multiplist Strategy for Strengthening Nonequivalent Control Group Designs. Evaluation Review, Dec 1987; vol. 11: pp. 691 – 71.

Abstract
Evaluation researchers are often confronted with less than optimal conditions in which to design studies. When this occurs, researchers may be forced to utilize relatively weak designs that do not rule out all threats to internal validity. Using archival data from a sales campaign for a state lottery, this article illustrates a multiplist strategy (Cook, 1985) in which several complementary designs are utilized to help rule out the four threats to internal validity associated with the frequently utilized nonequivalent control group design. Specific methods for addressing each of these threats and strengthening the basic nonequivalent control groups design are also illustrated.

(11.2) Cho, J., & Trent, A. (2006). Validity in qualitative research revisited. Qualitative Research, 6 (3): 319-340.

Abstract
Concerns with the issues of validity in qualitative research have dramatically increased. Traditionally, validity in qualitative research involved determining the degree to which researchers’ claims about knowledge corresponded to the reality (or research participants’ construction of reality) being studied. The authors note that recent trends have shown the emergence of two quite different approaches to the validity question within the literature on qualitative research. The authors categorize and label these ‘transactional’ validity and ‘transformational’ validity. While useful, the authors assert that neither approach is sufficient to meet the current needs of the field. The authors propose a recursive, process-oriented view of validity as an alternative framework.

(11.3) Amy B. Dellinger and Nancy L. Leech. Toward a Unified Validation Framework in Mixed Methods Research. Journal of Mixed Methods Research, Oct 2007; vol. 1: pp. 309-332.

Abstract
The primary purpose of this article is to further discussions of validity in mixed methods research by introducing a validation framework to guide thinking about validity in this area. To justify the use of this framework, the authors discuss traditional terminology and validity criteria for quantitative and qualitative research, as well as present recently published validity terminology for mixed methods research. The authors discuss the rationale for their framework and how it uni?es thinking about validity in mixed methods research. Finally, they discuss how the framework can be used.