S. A. Linton, G. Pfeiffer, E. F. Robertson, and N. Ruskuc,
Computing Transformation Semigroups.
J. Symbolic Comput. 33 (2002), 145-162.
This paper describes algorithms for computing the structure of finite
transformation semigroups. The algorithms depend crucially on a new data
structure for an R-class in terms of a group and an action. They
provide for local computations, concerning a single R-class, without
computing the whole semigroup, as well as for computing the global
structure of the semigroup. The algorithms have been implemented in the
share package MONOID within the GAP system for computational
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