@book { TheDevelopmentofaCommonFrameworkScaleofLanguageProficiency,
    title = "The Development of a Common Framework Scale of Language Proficiency",
    author = "Brian {North}",
    year = "2012",
    publisher = "Peter Lang Verlag",
    address = "New York, United States of America",
    doi = "10.3726/978-1-4539-1059-7",
    url = "https://www.peterlang.com/document/1054400"
}