Canonical Reduction of Mechanical Systems Invariant under Abelian Group Actions with an Application to Celestial Mechanics William Satzer, Jr. Indiana University Mathematics Journal 1977 text pdf 10.1512/iumj.1977.26.26077 10.1512/iumj.1977.26.26077 en Indiana Univ. Math. J. 26 (1977) 951 - 976 state-of-the-art mathematics http://iumj.org/access/