url:: https://ocw.mit.edu/courses/sloan-school-of-management/15-988-system-dynamics-self-study-fall-1998-spring-1999/readings/unexpected.pdf file:: https://www.dropbox.com/s/1bsz04wd3xg703x/Unexpected%20Behaviors%20in%20Higher-%20Order%20Positive%20Feedback%20Loops.pdf?dl=0