I’m working on a project where the researchers need a case-control study, though they may not know that yet. I want to show them what a case-control study gives them that would not be available with other methods. But I need to come up with a reasonable control group for the case-control design. It doesn’t have to be perfect, but it can’t be a totally stupid control group either. This article is the classic reference on the theoretical principles that underlie the selection of controls in a case-control study.
Wacholder S et al. Selection of Controls in Case-Control Studies. I. Principes. American Journal of Epidemiology 1992: 135(9); 1019-1028. Available at http://aje.oxfordjournals.org/content/135/9/1019.abstract.