Teoh, W. L., M. S. Fun, S. Y. Teh, M. B. C. Khoo, and W. C. Yeong. “EXACT RUN LENGTH DISTRIBUTION OF THE DOUBLE SAMPLING X-BAR CHART WITH ESTIMATED PROCESS PARAMETERS”. The South African Journal of Industrial Engineering, vol. 27, no. 1, May 2016, pp. 20-31, doi:10.7166/27-1-978.