@book { MethodenundCharakteristikaderMarktforschungviaInternet,
    title = "Methoden und Charakteristika der Marktforschung via Internet",
    author = "René {Mangold}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832452186",
    url = "https://m.diplom.de/document/220745"
}