@book { Mathematikfrkonomen,
    title = "Mathematik für Ökonomen",
    subtitle = "Grundlagen, Methoden und Anwendungen",
    author = "Alpha C. {Chiang} and Harald {Nitsch} and Kevin {Wainwright}",
    year = "2012",
    publisher = "Vahlen",
    address = "München, Deutschland",
    url = "https://vahlen.openpublishing.com/document/1220879"
}