@book { ProblemederArbeitsunfhigkeitsbescheinung,
    title = "Probleme der Arbeitsunfähigkeitsbescheinung",
    author = "Erik {Angel}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1090099"
}