@book { AgrarfrageundAufklrunginLettlandundEstland,
    title = "Agrarfrage und Aufklärung in Lettland und Estland",
    author = "Erich {Donnert}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1104864"
}