@book { GrundlagenPortrtundAktfotografie,
    title = "Grundlagen Porträt- und Aktfotografie",
    author = "Henrik {Pfeifer}",
    year = "2015",
    publisher = "humboldt",
    address = "Hannover, Deutschland",
    url = "https://schluetersche.openpublishing.com/document/403189"
}