Ammon, Ulrich. Status and Function of Languages and Language Varieties (inglizcha). Walter de Gruyter, 1989 — 422-bet. ISBN 978-3-11-086025-2. Qaraldi: 13-fevral 2021-yil. „By the term world language approximately the following can be understood: Firstly, [...]. Secondly, international planned languages (e.g Esperanto, Ido, Interlingua).“
de Mejía, Anne-Marie. Power, Prestige, and Bilingualism: International Perspectives on Elite Bilingual Education (inglizcha). Multilingual Matters, 2002 — 47–49-bet. ISBN 978-1-85359-590-5. „'international language' or 'world language' [...] The following languages of wider communication, that may be used as first or as second or foreign languages, are generally recognised: English, German, French, Spanish, Portuguese, Dutch, Arabic, Russian and Chinese.“
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Ammon, Ulrich (7-oktabr 2010-yil), Coupland, Nikolas (muh.), „World Languages: Trends and Futures“, The Handbook of Language and Globalization, Oxford, UK: Wiley-Blackwell, 101-bet, doi:10.1002/9781444324068.ch4, ISBN978-1-4443-2406-8{{citation}}: CS1 maint: date format ()