López-Cálix, J. R., Seligson, M., & Alcázar, L. (2009). Local accountability  and the Peruvian Vaso de Leche program. En S. D. Morris y Ch. H. Blake (Eds.), Corruption and democracy in Latin America (pp. 111-130). Pittsburgh: University of Pittsburgh Press.

This study seeks to avoid the weaknesses of prior work. Rather than comparing across space or across time, with all of the inherent limitations in establishing effective control variables, this study examines a single country, Peru, and a single time period, 2002, and focuses on a single program, the Vaso de Leche (glass of milk). It draws upon a detailed study of public expenditures that enable us to trace the use of public funds from their inception in the budget process down to the consumption of the glass of milk inside households, and in so doing take note of the points in the system in which the loss of the milk occurs. We do not need to make any questionable assumptions about control variables, since we are not varying the place or the time in which the study is being conducted.