@article{DimitrovaKoppitz2011,
  author    = {Dimitrova, Ilinka and Koppitz, J{\"o}rg},
  title     = {On the maximal regular subsemigroups of ideals of order-preserving or order-reversing transformations},
  series = {Semigroup forum},
  volume    = {82},
  journal   = {Semigroup forum},
  number    = {1},
  publisher = {Springer},
  address   = {New York},
  issn      = {0037-1912},
  doi       = {10.1007/s00233-010-9272-8},
  pages     = {172 -- 180},
  year      = {2011},
  abstract  = {We characterize the maximal regular subsemigroups of the ideals of the semigroup of all order-preserving transformations as well as of the semigroup of all order-preserving or order-reversing transformations on a finite ordered set.},
  language  = {en}
}
@article{DimitrovaKoppitz2022,
  author    = {Dimitrova, Ilinka and Koppitz, J{\"o}rg},
  title     = {On relative ranks of the semigroup of orientation-preserving transformations on infinite chain with restricted range},
  series = {Communications in algebra},
  volume    = {50},
  journal   = {Communications in algebra},
  number    = {5},
  publisher = {Taylor \& Francis Group},
  address   = {Philadelphia},
  issn      = {0092-7872},
  doi       = {10.1080/00927872.2021.2000998},
  pages     = {2157 -- 2168},
  year      = {2022},
  abstract  = {Let X be an infinite linearly ordered set and let Y be a nonempty subset of X. We calculate the relative rank of the semigroup OP(X,Y) of all orientation-preserving transformations on X with restricted range Y modulo the semigroup O(X,Y) of all order-preserving transformations on X with restricted range Y. For Y = X, we characterize the relative generating sets of minimal size.},
  language  = {en}
}