Zhang B, Liu W, Lemon SC, Barton BA, Fischer MA, Lawrence C, Rahn EJ, Danila MI, Saag KG, Harris PA, Allison JJ. Design, analysis, power, and sample size calculation for three-phase interrupted time series analysis in evaluation of health policy interventions. J Eval Clin Pract. 2020 Jun; 26(3):826-841.