@book{Mertens2018,
  author    = {Mertens, Konrad},
  title     = {Photovoltaics - Fundamentals, Technology, and Practice},
  edition   = {2. Edition},
  publisher = {John Wiley \& Sons, Inc.},
  address   = {Chichester, UK},
  isbn      = {978-1-119-40104-9},
  publisher      = {FH M{\"u}nster - University of Applied Sciences},
  pages     = {347},
  year      = {2018},
  language  = {en}
}
@book{Mertens2018,
  author    = {Mertens, Konrad},
  title     = {Photovoltaik - Lehrbuch zu Grundlagen, Technologie und Praxis, 4., aktualisierte Auflage},
  publisher = {Carl Hanser Verlag},
  address   = {M{\"u}nchen},
  isbn      = {978-3-446-44863-6},
  publisher      = {FH M{\"u}nster - University of Applied Sciences},
  pages     = {383},
  year      = {2018},
  language  = {de}
}
@book{Poppe2018,
  author    = {Poppe, Martin},
  title     = {Pr{\"u}fungstrainer Elektrotechnik},
  edition   = {3},
  publisher = {Springer},
  address   = {Heidelberg},
  isbn      = {9783662566480},
  doi       = {10.1007/978-3-662-56649-7},
  pages     = {344},
  year      = {2018},
  language  = {mul}
}