Greberg, Jenny, and Abubakary Salama. “Analysis of the Current Challenges for Deep Underground Mines: Labour Productivity Improvement”. Tanzania Journal of Engineering and Technology 39, no. 1 (June 30, 2020): 32-46. Accessed May 4, 2024. https://tjet.udsm.ac.tz/index.php/tjet/article/view/517.