@book { PDF,
    title = "В защиту Льва Троцкого (PDF)",
    author = "Дэвид {Норт (David North)}",
    year = "2018",
    publisher = "MEHRING Verlag",
    address = "Essen, Deutschland",
    url = "https://mehring.openpublishing.com/document/425635"
}