@book { MarktanalysezurErffnungeinesGesundheitsstudiosinHamburg,
    title = "Marktanalyse zur Eröffnung eines Gesundheitsstudios in Hamburg",
    author = "Jan {Klein}",
    year = "2018",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    url = "https://www.hausarbeiten.de/document/412853"
}