Applying rewriting methods to special monoids
Louxin Zhang · Mathematical Proceedings of the Cambridge Philosophical Society · 1992
A special monoid is a monoid presented by generators and defining relations of the form w = e, where w is a non-empty word on generators and e is the empty word. Groups are special monoids. But there exist special monoids that are not groups. Special monoids have been extensively studied by Adjan[1] and Makanin[7] (see also [2]).