https://www.taylorfrancis.com/chapters/edit/10.4324/9780203761793-2/optimum-growth-theory-social-time-preference-1-computerised-mathematical-modelling-exercise-choose-social-discount-rate-2-sardar-islam?context=ubx&refId=87c38d91-080c-4ca1-892f-9cc7649a5c21