Source: https://www.researchgate.net/publication/287928707_What_is_the_place_of_diaphasical_diatopical_and_diastratical_variation_in_the_Common_European_Framework_of_Reference_for_Languages/fulltext/567a7bd908aeaa48fa4c404d/287928707_What_is_the_place_of_diaphasical_diatopical_and_diastratical_variation_in_the_Common_European_Framework_of_Reference_for_Languages.pdf