Hunker, Louisa. "Pits in Potosi". The Leader. National Outdoor Leadership School. Archived from the original on 31 August 2006. Retrieved 12 April 2007.
Hunker, Louisa. "Pits in Potosi". The Leader. National Outdoor Leadership School. Archived from the original on 31 August 2006. Retrieved 12 April 2007.