@book { Philosophiaperennis,
    title = "Philosophia perennis",
    subtitle = "Erich Heintel zum 80. Geburtstag- (2 Teile)",
    author = "Hans-Dieter {Klein} and Johann {Reikerstorfer}",
    year = "1994",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1113940"
}