@book { TheorienzuAktivittFitnessundGesundheit,
    title = "Theorien zu Aktivität - Fitness und Gesundheit",
    author = "Sebastian {Runkel}",
    year = "2009",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640440528",
    url = "https://www.hausarbeiten.de/document/136157"
}