@book { SprachatlasOstserbiensundWestbulgariensI,
    title = "Sprachatlas Ostserbiens und Westbulgariens (I)",
    author = "Andrej N. {Sobolev}",
    year = "1998",
    publisher = "Biblion",
    address = ", Germany",
    doi = "10.3726/b12867",
    url = "https://www.peterlang.com/document/1087712"
}