This paper led to the realization that chaos was actually a common phenomenon in physical systems, as well as popularizing the term "chaos".

A special case of our main result says that if there is a periodic point with period 3, then for each integern= 1, 2, 3, ..., there is a periodic point with periodn. Furthermore, there is an uncountable subset of pointsxinJwhich are not even "asymptotically periodic."--Li & Yorke, "Period Three Implies Chaos"

American Mathematical Monthly, Vol. 82 No. 10, 985-992.