@book { ExperimentelleAnalysederWirkungenausgewhlterDirektmarketingInstrumente,
    title = "Experimentelle Analyse der Wirkungen ausgewählter Direktmarketing-Instrumente",
    author = "Michael {Ahrens}",
    year = "2018",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b13604",
    url = "https://www.peterlang.com/document/1068209"
}