@book { MentaleTechnikeninderKundenberatung,
    title = "Mentale Techniken in der Kundenberatung",
    author = "Angela {Sekli}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1095382"
}