In 1368 the Ming dynasty began its rule. The location of the capital changed from Dadu (modern Beijing) to Nanjing (1368–1421), and later back to Beijing (1421–1644). Because of the different locations of the capital and other issues related to the standard pronunciation, the question of which dialect served as a foundation for the standard pronunciation has been a point of strong interest to researchers. In 1375 the rhyme dictionary Hóngwǔ Zhèngyùn 洪武正韻 was compiled at the order of the first Ming emperor. In the fifteenth century Korean scholars made a great effort to transcribe this prestigious phonological work into the newly invented Hangul spellings. The result was the Hóngwǔ Zhèngyùn Yìxùn 洪武正韻譯訓, finished in 1451 with a revision in 1455. The Hóngwǔ Zhèngyùn Yìxùn provides phonetic values for the phonology of the Hóngwǔ Zhèngyùn. The Xīrú Ěrmù Zī 西儒耳目資 ‘An Aid to the Eyes and Ears of Western Literati’ of 1626 by Nicolas Trigault (1577–1628) represents one of the earliest efforts to transcribe an entire Chinese phonology into an alphabetical system without referring to Chinese rhyme works.