@book { DasProblemdersukzessivenBeihilfe,
    title = "Das Problem der sukzessiven Beihilfe",
    author = "Heiko Hartmut {Lesch}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1080212"
}