Johnston, Marston, and Rodney L Stevens. “A Systematic Approach to Analyzing Environmental Issues Involving Complex Systems (a Web-Based Course)”. Ecocycles 1, no. 2 (September 3, 2015): 46–50. Accessed March 3, 2021. https://www.ecocycles.net/ojs/index.php/ecocycles/article/view/38.