@incollection{WaKlC08a,
  author = {Wagner, R. and Klaus, M.},
  title = {{C}ultural {I}mpacts on the {S}pread of {M}obile {C}ommerce: {A}n {I}nternational {C}omparison},
  booktitle = {{H}andbook of {R}esearch on {M}obile {B}usiness},
  publisher = {{I}{G}{I}},
  year = {2008},
  pages = {245 - 259},
  edition = {2},
  url = {http://www.igi-global.com/downloads/pdf/Unhelkar245.pdf}
}

@incollection{WaKlC08b,
  author = {Wagner, R. and Klaus, M.},
  title = {{M}obile {D}irect {M}arketing},
  booktitle = {{H}andbook of {R}esearch on {M}obile {B}usiness},
  publisher = {{I}{G}{I}},
  year = {2008},
  pages = {269 - 281},
  edition = {2},
  url = {http://books.google.de/books?hl=de&lr=&id=JlpFnu8hMK4C&oi=fnd&pg=PA269&dq=martin+klaus+%22ralf+Wagner%22&ots=GXB0O_sNC_&sig=Jdr05yCvx_U5h4YlXX9EGVWOioU#PPA269,M1}
}

@techreport{WaKlW08b,
  author = {Wagner, R. and Klaus, M.},
  title = {{C}hallenges and {E}xamples of {M}obile {D}irect {M}arketing},
  year = {2008},
  number = {2}
}

@techreport{WaKlW08a,
  author = {Wagner, R. and Klaus, M.},
  title = {{T}he {S}pread of {M}obile {C}ommerce: An {I}nter-{C}ultural {C}omparison},
  year = {2008},
  number = {4},
  url = {http://books.google.de/books?hl=de&lr=&id=JlpFnu8hMK4C&oi=fnd&pg=PA245&dq=%22martin+klaus%22+%22ralf+wagner%22&ots=GXB0O_sQAV&sig=7582ynvDxyqaAmisdbVdaryUkGk}
}