Ray 1987, с. 66. Ray, Haraprasad. An Analysis of the Chinese Maritime Voyages into the Indian Ocean During Early Ming Dynasty and Their Raison d'Etre // China Report 23 (1). 1987. DOI:10.1177/000944558702300107. p. 65 – 87. (на английски)
Needham 1971, с. 460 – 470. Needham, Joseph. Science and Civilization in China. Volume 4, Physics and physical technology. Part III, Civil engineering and nautics. Cambridge, England, Cambridge University Press, 1971. OCLC 634783184. (на английски)
Needham 1971, с. 452. Needham, Joseph. Science and Civilization in China. Volume 4, Physics and physical technology. Part III, Civil engineering and nautics. Cambridge, England, Cambridge University Press, 1971. OCLC 634783184. (на английски)