Singh, Housila P., and Tanveer A. Tarray. “A Stratified Mangat and Singh’s Optional Randomized Response Model Using Proportional and Optimal Allocation”. Statistica 74, no. 1 (January 1, 2014): 65–83. Accessed May 18, 2022. https://rivista-statistica.unibo.it/article/view/4598.