@phdthesis{Sponholz1988,
  author      = {Barbara Sponholz},
  title       = {Karsterscheinungen in nichtkarbonatischen Gesteinen der {\"o}stlichen Republik Niger},
  type        = {doctoralthesis},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year        = {1988},
}