@article{DimitrovaKoppitz2012,
  author    = {Dimitrova, Ilinka and Koppitz, J{\"o}rg},
  title     = {On the monoid of all partial order-preserving extensive transformations},
  series = {Communications in algebra},
  volume    = {40},
  journal   = {Communications in algebra},
  number    = {5},
  publisher = {Taylor \& Francis Group},
  address   = {Philadelphia},
  issn      = {0092-7872},
  doi       = {10.1080/00927872.2011.557813},
  pages     = {1821 -- 1826},
  year      = {2012},
  abstract  = {A partial transformation alpha on an n-element chain X-n is called order-preserving if x <= y implies x alpha <= y alpha for all x, y in the domain of alpha and it is called extensive if x <= x alpha for all x in the domain of alpha. The set of all partial order-preserving extensive transformations on X-n forms a semiband POEn. We determine the maximal subsemigroups as well as the maximal subsemibands of POEn.},
  language  = {en}
}
@article{DimitrovaFernandesKoppitz2012,
  author    = {Dimitrova, Ilinka and Fernandes, Vitor H. and Koppitz, J{\"o}rg},
  title     = {The maximal subsemigroups of semigroups of transformations preserving or reversing the orientation on a finite chain},
  series = {Publicationes mathematicae},
  volume    = {81},
  journal   = {Publicationes mathematicae},
  number    = {1-2},
  publisher = {Institutum Mathematicum Universitatis Debreceniensis, Debreceni Tudom{\´a}nyegyetem Matematikai Int{\´e}zete},
  address   = {Debrecen},
  issn      = {0033-3883},
  doi       = {10.5486/PMD.2012.4897},
  pages     = {11 -- 29},
  year      = {2012},
  abstract  = {The study of the semigroups OPn, of all orientation-preserving transformations on an n-element chain, and ORn, of all orientation-preserving or orientation-reversing transformations on an n-element chain, has began in [17] and [5]. In order to bring more insight into the subsemigroup structure of OPn and ORn, we characterize their maximal subsemigroups.},
  language  = {en}
}
@unpublished{KoppitzMusunthia2012,
  author    = {Koppitz, J{\"o}rg and Musunthia, Tiwadee},
  title     = {Maximal subsemigroups containing a particular semigroup},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-57465},
  year      = {2012},
  abstract  = {We study maximal subsemigroups of the monoid T(X) of all full transformations on the set X = N of natural numbers containing a given subsemigroup W of T(X), where each element of a given set U is a generator of T(X) modulo W. This note continues the study of maximal subsemigroups of the monoid of all full transformations on an infinite set.},
  language  = {en}
}