shojai, M., Kazemnejad, A., Zayeri, F. and Vahedi, M. (2013) “Application of semi-parametric single-index two-part regression and parametric two-part regression in estimation of the cost of functional gastrointestinal disorders”, Gastroenterology and Hepatology from Bed to Bench, 6(4), pp. Gastroenterol Hepatol Bed Bench 2013;6(4):202–209. doi: 10.22037/ghfbb.v6i4.439.