@book { KundenzufriedenheitsmessungmittelsFragebogen,
    title = "Kundenzufriedenheitsmessung mittels Fragebogen",
    author = "Manfred {Hammerl}",
    year = "2007",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638892223",
    url = "https://www.hausarbeiten.de/document/84141"
}