@book{Engels2009,
  author    = {Engels, Christoph},
  title     = {Basiswissen Business Intelligence},
  publisher = {W3L-Verlag},
  address   = {Herdecke},
  isbn      = {978-3-937137-37-7},
  pages     = {VIII, 200},
  year      = {2009},
  language  = {de}
}
@incollection{EngelsJendernalikKienle2012,
  author    = {Engels, Christoph and Jendernalik, Lars and Kienle, Andrea},
  title     = {Smart planning},
  series = {Smart Energy 2012 : Wie smart ist der Weg zur Energiewende?},
  publisher = {H{\"u}lsbusch},
  address   = {Gl{\"u}ckstadt},
  pages     = {13},
  year      = {2012},
  language  = {de}
}
@article{B{\"a}ckEngelsGaul2010,
  author    = {B{\"a}ck, Thomas and Engels, Christoph and Gaul, Armin J.},
  title     = {Optimales Asset Management},
  series = {Energiewirtschaftliche Tagesfragen},
  number    = {01. Feb},
  issn      = {0720-6240},
  pages     = {4},
  year      = {2010},
  language  = {de}
}