Murphy, T. E., P. V. Ness, K. Araujo, and M. Pisani. “An Empirical Method of Detecting Time-Dependent Confounding: An Observational Study of Next Day Delirium in a Medical ICU”. International Journal of Statistics in Medical Research, vol. 5, no. 1, Jan. 2016, pp. 41-47, doi:10.6000/1929-6029.2016.05.01.4.