元史
There is no scholarly consensus on what specific territory "Liuqiu" refers to in the "Book of Sui" and "History of Yuan". Chang Biyu notes that "Some scholars believe that the record of 'Liuqiu' referred to Taiwan, while some say it was a reference to what are now the Ryukyu Islands ... and others suggest that it was a general term referring to islands in the East China Sea and nearby waters".