@book { KopulaAuxiliarPrdikativ,
    title = "Kopula, Auxiliar, Prädikativ",
    author = "Hagen {Pitsch}",
    year = "2018",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b12286",
    url = "https://www.peterlang.com/document/1110526"
}