Birgit Reinert Dirk Zeckzer MRC - Data Structures and Procedures for Computing in Monoid and Group Rings. 41-78 1999 10 Appl. Algebra Eng. Commun. Comput. 1 http://link.springer.de/link/service/journals/00200/bibs/9010001/90100041.htm db/journals/aaecc/aaecc10.html#ReinertZ99