@phdthesis{Lehnert2014,
  author      = {Ralf Lehnert},
  title       = {On the critical exponent of infinitely generated Veech groups},
  type        = {doctoralthesis},
  pages       = {83},
  school      = {Universit{\"a}tsbibliothek Johann Christian Senckenberg},
  year        = {2014},
}