(1) Babbel Magazine (24 April 2016). The 10 Most Spoken Languages In The World. Retrieved from https://www.babbel.com/en/magazine/the-10-most-spoken-languages-in-the-world/
(2) 世界の言語ランキング【決定版】！最強の言語【TOP10】を紹介します。E-student. Retrieved from https://e-student-ph.com/worldwide-languages-ranking-1780.html
(3) Ministry of Education, Culture, Sports, Science and Technology(MEXT) (no date).文部科学省 基礎データ. Retrieved from http://www.mext.go.jp/b_menu/shingi/chukyo/chukyo3/015/siryo/attach/1379917.htm
(1) Study.com (no date). What is a lingua franca? - Definition & examples. Retrieved from https://study.com/academy/lesson/what-is-a-lingua-franca-definition-examples.html
(2) Logos and Mythos (13 March 2018).【語源学】 リンガ・フランカとは何か？その由来と歴史. Retrieved from https://tokoshie-jp.com/2018/03/13/etymology-lingua-franca/
(3) Debate. org (no date). Should there be one global language? Retrieved from https://www.debate.org/opinions/should-there-be-one-global-language
(4) BBC News Japan (29 May 2018). 英語はこれからも世界の「共通語」でいられるのか. Retrieved from https://www.bbc.com/japanese/features-and-analysis-44220537
(1) YouTube (19 November 2014). Why has English developed as a world language? FutureLearn. Retrieved from https://www.youtube.com/watch?v=kg8jS-AMyMo
(2) The Japan Times (August 17 2014). Could the lingua franca approach to learning break Japan’s English curse? Retrieved from https://www.japantimes.co.jp/community/2014/08/17/issues/could-the-lingua-franca-approach-to-learning-break-japans-english-curse/#.W8PB6BMzau4
(3) アジアの英語教育は日本に比べて優れてる？ 在日外国人に直撃インタビュー English lab https://www.rarejob.com/englishlab/column/20180719/
(4) アジアの英語教育事情 本多 功 http://ocean-gnet.com/images/pdf/asia_jijyou.pdf
(5) The History of English (no date). English as a global language. Retrieved from https://www.thehistoryofenglish.com/issues_global.html
(6) 英語が国際言語といわれるのはなぜか 小野礼子 https://www.kaisei.ac.jp/wp-content/uploads/library/pdf/44_09_r_ono.pdf
(7)「国際語」 へと変貌する英語 本名信行 https://berd.benesse.jp/berd/center/open/berd/backnumber/2006_05/fea_honna_01.html
(8) これからの言葉〜グローバル時代の言語は多言語だ トム・ガリー http://www.c.u-tokyo.ac.jp/info/about/booklet-gazette/bulletin/564/open/B-5-1.html
(9) 鈴木雅光 (2004). なぜグローバル語なのか 東洋大学学術情報リポジトリ規程/Toyo University Repository for Academic Resources. Retrieved from https://toyo.repo.nii.ac.jp/?action=pages_view_main&active_action=repository_view_main_item_detail&item_id=5150&item_no=1&page_id=13&block_id=17
(1) BBC (22 February 2012). Is English or Mandarin the language of the future? Retrieved from https://www.bbc.com/news/magazine-17105569
(2) History in an Hour (15 December 2013). Will Chinese Overtake English As The Lingua Franca?
(3) History Says Yes (no date). Retrieved from http://www.historyinanhour.com/2013/12/15/chinese-or-english-as-the-lingua-franca/
(4) BBC News Japan (29 May 2018). 英語はこれからも世界の「共通語」でいられるのか. Retrieved from https://www.bbc.com/japanese/features-and-analysis-44220537
(5) 中国経済が世界一になる時、中国語は国際共通語になるのか？https://kaigai.life/?p=970
(6) ２１世紀、中国語は英語に代わる「世界の共通語」になるか＝中国メディア Searchina http://news.searchina.net/id/1622924?page=1
(1) El Pais (30 April 2013). What is the world role of Spanish? Retrieved from https://elpais.com/elpais/2013/04/30/inenglish/1367320944_963514.html
(2) Language Magazine (28 November 2019). Spanish in the World. https://www.languagemagazine.com/2019/11/18/spanish-in-the-world/
(3) The Citizen Tanazania (n.d.). Embassy: Spanish on the way to become a global universal language. http://www.exteriores.gob.es/Embajadas/DARESSALAAM/en/Documents/SPANISH.pdf
(4) El Pais (2018, July 5). Number of Spanish speakers tops 577 million. https://english.elpais.com/elpais/2018/07/05/inenglish/1530780465_701866.html
(5) The Language and Life Project (n.d.). Spanish Voices. https://languageandlife.org/documentaries/spanish-voices/
(6) El Pais (2014, September 24). The race to save Mexico’s dying languages. https://english.elpais.com/elpais/2014/09/23/inenglish/1411484950_125474.html
(1) World Economic Forum (26 October 2018). French is now the fifth most spoken world language and growing—thanks to Africans. Retrieved from https://www.weforum.org/agenda/2018/10/french-is-now-the-fifth-most-spoken-world-language-and-growing-thanks-to-africans/
(2) The Guardian (2 December 2017). French the new lingua franca of the world – vraiment? Retrieved from https://www.theguardian.com/commentisfree/2017/dec/02/french-language-world-lingua-franca-emmanuel-macron-optimism-grandiose
(3) multilingirl (no date). 世界中でフランス語が認められる理由 TOP10 と、私がフランス語を勉強している理由. Retrieved from https://www.multilingirl.com/2016/04/why-french-language-is-broadly-accepted.html