Sengupta, Sohini, Douglas W. Chung, Ramdhir Kumar, Paritosh Gupta, Sonu Upadhyay, and Ashok Rattan. “Sigma Metrics As Quality Indicators in Guiding and Tracking Laboratory Process Improvement”. International Journal of Research in Medical Sciences 12, no. 1 (December 12, 2023): 75–81. Accessed October 13, 2025. https://www.msjonline.org/index.php/ijrms/article/view/13028.