@book { ClassroomObservation,
    title = "Classroom Observation",
    author = "Friedrich {Lenz} and Maximiliane {Frobenius} and Revert {Klattenberg}",
    year = "2020",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1057587"
}