参考資料

https://royalediting.com/the-usage-of-the-definite-article-rules-and-exceptions

https://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv255.shtml

https://www.quora.com/Why-did-some-languages-develop-a-definite-article-while-others-didnt?share=1

https://en.wikipedia.org/wiki/Proto-Germanic_language

https://en.m.wikibooks.org/wiki/Old_English/Articles

https://en.wikipedia.org/wiki/Old_English_grammar

https://en.wikipedia.org/wiki/Old_English

https://en.wikipedia.org/wiki/Middle_English#Early_Middle_English

https://www.etymonline.com/word/the

https://en.m.wikibooks.org/wiki/Old_English/Articles

http://www.lattice.cnrs.fr/IMG/pdf/Handbook.gramma.2010.pdf

https://dspace.unive.it/bitstream/handle/10579/2584/815421-1165049.pdf;sequence=2

Definiteness by Christopher Lyons (Cambridge Textbooks in Linguistics)