@book { ZufriedenheitmitDienstleistungen,
    title = "Zufriedenheit mit Dienstleistungen",
    author = "Andreas {Siefke} and  {Universität Münster}",
    year = "2018",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b13656",
    url = "https://www.peterlang.com/document/1068244"
}