@book { DerdemographischeWandelinDeutschland,
    title = "Der demographische Wandel in Deutschland",
    author = "Tim  {Mehlig}",
    year = "2011",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640955428",
    url = "https://www.hausarbeiten.de/document/174888"
}