@book { Bulgarien1300,
    title = "Bulgarien 1300",
    subtitle = "Referate der Sektion Sprache und Literatur des Symposiums Bulgarien in Geschichte und Gegenwart, Hamburg, 9.-17. 9. 1981",
    author = "Peter {Hill}",
    year = "1982",
    publisher = "Biblion",
    address = ", Germany",
    doi = "10.3726/b12468",
    url = "https://www.peterlang.com/document/1066938"
}