@unpublished{Doherr2009,
  author    = {Doherr, Detlev},
  title     = {Geothermal Energy in Germany},
  series    = {European geologist : revue de la F{\´e}d{\´e}ration Europ{\´e}enne des G{\´e}ologues},
  volume    = {2009},
  number    = {27},
  issn      = {1028-267X},
  url       = {https://eurogeologists.eu/wp-content/uploads/2017/08/a_Magazine-May2009.pdf},
  institution = {Fakult{\"a}t Maschinenbau und Verfahrenstechnik (M+V)},
  pages     = {25 -- 26},
  year      = {2009},
  language  = {en}
}