Carver, S., Beatty, J., Troyer, R., Harris, R., Stutzman-Rodriguez, K., Barrs, V., Chan, C., Tasker, S., Lappín, M., & VandeWoude, S. (2015). Closing the gap on causal processes of infection risk from cross-sectional data: structural equation models to understand infection and co-infection. : BioMed Central.