@Article{	  die86tcs,
  author	= "Volker Diekert",
  journal	= "Theoretical Computer Science",
  pages		= "199--208",
  title		= "Complete semi-{T}hue systems for abelian groups",
  volume	= "44",
  year		= "1986",
  abstract	= "We show that there are infinitely many examples of finite
		  semi-Thue systems with decidable word problem and which
		  have no finite equivalent noetherian and confluent
		  (=complete) reduction system. These examples have a very
		  simple algebraic structure: they are abelian groups. More
		  precisely, we develop necessary and sufficient conditions
		  for the existence of complete semi-Thue systems for
		  presentations of finitely generated abelian groups.",
  doi		= "10.1016/0304-3975(86)90117-9"
}