@book { BeziehungsundKontaktmanagement,
    title = "Beziehungs- und Kontaktmanagement",
    subtitle = "Die Möglichkeiten und die Realität",
    author = "Guido {Jahnke}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832435493",
    url = "https://m.diplom.de/document/219210"
}