A Dual Methodology for Case Studies: Synergistic Use of a Longitudinal Single Site with Replicated Multiple Sites
提出一种结合实时纵向研究与回顾性多案例研究的双重方法论，通过互补优势增强数据收集与分析，并提升构念、内部和外部三种效度，适合研究动态现象。
This paper describes a case study methodology that combines a real-time longitudinal (three-year) study with nine retrospective case studies about the same phenomenon. These two kinds of case studies offer opportunities for complementary and synergistic data gathering and analysis. That is, specific strengths in each method compensate for some particular weakness in the other. For instance, the retrospective studies offer the opportunity to identify patterns indicative of dynamic processes and the longitudinal study provides a close-up view of those patterns as they evolve over time. The combination of the two types of case studies also enhances three kinds of validity: construct, internal and external. The author also discusses problems with and shortcomings of this dual methodology and suggests the circumstances for which the methodology is especially appropriate.