@book { EGkoAuditVerordnung,
    title = "EG-Öko-Audit-Verordnung",
    author = "Thomas {Ziegler}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832439873",
    url = "https://m.diplom.de/document/219624"
}