@book { PrdikatenlogikohnegebundeneVariablen,
    title = "Prädikatenlogik ohne gebundene Variablen",
    author = "Jürgen {Bartnick}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1072408"
}