@book { FranzHettingersGrundlegungeinerchristlichenApologetik,
    title = "Franz Hettingers Grundlegung einer christlichen Apologetik",
    author = "Agnes {Hufnagel}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1089638"
}