@book { PaulTillich,
    title = "Paul Tillich",
    subtitle = "Sein Leben",
    author = "Renate {Albrecht} and Werner {Schüssler}",
    year = "1994",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1113941"
}