Another good reference is . Rubin invented a lot of observational data methods for correcting to measure causal effect. Imbens is also a prolific author in this area, and even just googling for propensity model papers from Imbens will leads to many methods and many other papers.
: < http://www.stat.columbia.edu/~gelman/arm/ >
: < https://www.amazon.com/Causal-Inference-Statistics-Biomedica... >