@book { DasGeheimnisdesZyklotrons,
    title = "Das Geheimnis des Zyklotrons",
    author = "Freder {van Holk}",
    year = "2019",
    publisher = "Uksak E-Books",
    address = "Lengerich, Germany",
    url = "https://uksakebooks.grin.com/document/503641"
}