@article{GroteSchmidt1989,
  author    = {Grote, H.-W. and Schmidt, Th.},
  title     = {Gaserstbef{\"u}llung einer Gasspeicherkaverne.},
  series = {gwf-Gas/Erdgas},
  volume    = {130},
  journal   = {gwf-Gas/Erdgas},
  number    = {5},
  pages     = {238 -- 242},
  year      = {1989},
  language  = {de}
}
@article{HaertnagelSchaalSchmidt1989,
  author    = {H{\"a}rtnagel, R. and Schaal, W. and Schmidt, Th.},
  title     = {Erdgasspeicherung in Xanten. Anlage zur unterirdischen Speicherung von Erdgas in Kavernen.},
  series = {Bergbau},
  volume    = {40},
  journal   = {Bergbau},
  number    = {8},
  pages     = {392 -- 397},
  year      = {1989},
  language  = {de}
}