@book { DeutscheSprachinselnweltweitInterneundexternePerspektivenGermanLanguageVarietiesWorldwideInternalandexternalPerspectives, title = "Deutsche Sprachinseln weltweit: Interne und externe Perspektiven- German Language Varieties Worldwide: Internal and external Perspectives", author = "William {Keel} and Klaus J. {Mattheier}", year = "2003", publisher = "Peter Lang Verlag", address = "Berlin, Germany", url = "https://www.peterlang.com/document/1095063" }