Binary Collision Modeling Garrett BirkhoffJerome Eckerman Indiana University Mathematics Journal 1963 text pdf 10.1512/iumj.1963.12.12034 10.1512/iumj.1963.12.12034 en Indiana Univ. Math. J. 12 (1963) 543 - 556 state-of-the-art mathematics http://iumj.org/access/