@book { SteuerungvonMarkenportfolios,
    title = "Steuerung von Markenportfolios",
    author = "Martin {Koers}",
    year = "2018",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b13642",
    url = "https://www.peterlang.com/document/1068240"
}