@book { HamburgerVerkehr,
    title = "Hamburger Verkehr",
    author = "Gunter {Gerlach}",
    year = "2014",
    publisher = "hey! publishing",
    address = "München, Deutschland",
    doi = "10.3239/9783942822930",
    url = "https://www.heypublishing.com/document/267444"
}