@book { SprachlehrforschungTheorieundEmpirie,
    title = "Sprachlehrforschung: Theorie und Empirie",
    author = "Annette {Berndt} and Karin {Kleppin}",
    year = "2015",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/978-3-653-05628-0",
    url = "https://www.peterlang.com/document/1054116"
}