@book { RegionalanalysedesFitnessmarktesOstdeutschland,
    title = "Regionalanalyse des Fitnessmarktes Ostdeutschland",
    author = "André {Schulz}",
    year = "2004",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832479855",
    url = "https://m.diplom.de/document/223010"
}