@book { UmweltmanagementnachISO14001,
    title = "Umweltmanagement nach ISO 14001",
    author = "Patric {Langer}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832432584",
    url = "https://m.diplom.de/document/218945"
}