@Book{Stratmann.2001,
  author = {Stratmann, Jörg},
  title  = {Bedarfsgerechte Informationsversorgung im Rahmen eines produktlebenszyklusorientierten Controlling},

  year   = {2001},
  number = {},
  url    = {http://www.gbv.de/dms/hebis-darmstadt/toc/98415638.pdf},

  const  = {\ text}
}
@Inproceedings{ls_leimeister,
  author = {Berkovich, M. and Leimeister, J. M. and Krcmar, H.},
  title  = {Suitability of product development methods for hybrid products as bundles of classic products, software and service elements},

  year   = {2009},
  number = {},
  url    = {http://pubs.wi-kassel.de/wp-content/uploads/2013/05/JML_181.pdf},

  const  = {\ text}
}