@article{GraeterSperner2015,
  author    = {Graeter, Joachim and Sperner, Robert P.},
  title     = {On embedding left-ordered groups into division rings},
  series = {Forum mathematicum},
  volume    = {27},
  journal   = {Forum mathematicum},
  number    = {1},
  publisher = {De Gruyter},
  address   = {Berlin},
  issn      = {0933-7741},
  doi       = {10.1515/forum-2012-0070},
  pages     = {485 -- 518},
  year      = {2015},
  language  = {en}
}
@article{BrungsGraeter2017,
  author    = {Brungs, Hans H. and Gr{\"a}ter, Joachim},
  title     = {On central extensions of SL(2, F) admitting left-orderings},
  series = {Journal of Algebra},
  volume    = {486},
  journal   = {Journal of Algebra},
  publisher = {Elsevier},
  address   = {San Diego},
  issn      = {0021-8693},
  doi       = {10.1016/j.jalgebra.2017.05.025},
  pages     = {288 -- 327},
  year      = {2017},
  abstract  = {For an arbitrary euclidean field F we introduce a central extension (G(F), Phi) of SL(2, F) admitting a left-ordering and study its algebraic properties. The elements of G(F) are order preserving bijections of the convex hull of Q in F. If F = R then G(F) is isomorphic to the classical universal covering group of the Lie group SL(2, R). Among other results we show that G(F) is a perfect group which possesses a rank 1 cone of exceptional type. We also prove that its centre is an infinite cyclic group and investigate its normal subgroups.},
  language  = {en}
}