@article{ShtrakovKoppitz2016,
  author    = {Shtrakov, Slavcho and Koppitz, J{\"o}rg},
  title     = {Stable varieties of semigroups and groupoids},
  series = {Algebra universalis},
  volume    = {75},
  journal   = {Algebra universalis},
  publisher = {Springer},
  address   = {Basel},
  issn      = {0002-5240},
  doi       = {10.1007/s00012-015-0359-7},
  pages     = {85 -- 106},
  year      = {2016},
  abstract  = {The paper deals with Sigma-composition and Sigma-essential composition of terms which lead to stable and s-stable varieties of algebras. A full description of all stable varieties of semigroups, commutative and idempotent groupoids is obtained. We use an abstract reduction system which simplifies the presentations of terms of type tau - (2) to study the variety of idempotent groupoids and s-stable varieties of groupoids. S-stable varieties are a variation of stable varieties, used to highlight replacement of subterms of a term in a deductive system instead of the usual replacement of variables by terms.},
  language  = {en}
}