@book { RealEstateMarketing,
    title = "Real Estate Marketing",
    author = "Bettina {Knirsch}",
    year = "2000",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638958356",
    url = "https://www.hausarbeiten.de/document/97383"
}