K. Kamau, Simon, et al. “Challenges of Performance Appraisal Implementation and Their Effects on Service Delivery in Public Secondary Schools in Githunguri Sub-County of Kiambu County, Kenya”. American Scientific Research Journal for Engineering, Technology, and Sciences, vol. 49, no. 1, Dec. 2018, pp. 175-91, https://www.asrjetsjournal.org/American_Scientific_Journal/article/view/4513.