@book { KundenbezogeneKennzahlenKonzeption,
    title = "Kundenbezogene Kennzahlen - Konzeption",
    author = "Mario {Pichler}",
    year = "2001",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638979078",
    url = "https://www.hausarbeiten.de/document/99463"
}