Terbrugge, P.J., and R. Armstrong. “Vertical Pit Mining – an Alternative to Open Pit Mining for Massive Shallow Orebodies”. International Kimberlite Conference: Extended Abstracts 11 (September 18, 2017). Accessed February 12, 2026. https://journals.library.ualberta.ca/ikcabstracts.com/index.php/ikc/article/view/4013.