Adewale F. Lukman, Oyedeji Janet, and Abiola Racheal. “Modified Pena’s Measure for Detecting Influential Observations in Biased Estimators”. Zimbabwe Journal of Science and Technology, vol. 11, no. 1, Nov. 2016, pp. 58-65, https://journals.nust.ac.zw/index.php/zjst/article/view/92.