@book { DiefreiwilligeGesellschaft,
    title = "Die freiwillige Gesellschaft",
    subtitle = "Über das Ehrenamt in Deutschland",
    author = "Peter {Nitschke}",
    year = "2005",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1098989"
}