1. ; In: A Biodegradable Fiber Made of Polylactic Acid, Proceedings of the 35th International Man-Made Fiber Congress, Dornbirn, Austria, September 25-27, 1996; �sterreichisches Chemiefaser-Institut; pp. 1-10.
2. ; ; The Feynman Lectures on Physics, 6th ed.; Addison-Wesley: Reading, MA, 1963; Vol. 1, pp. 33-8-33-9.