The exact nature of relations between Tibet and the Ming dynasty of China (1368–1644) is unclear. Analysis of the relationship is further complicated by modern political conflicts and the application of Westphalian sovereignty to a time when the concept did not exist. Some Mainland Chinese scholars, such as Wang Jiawei and Nyima Gyaincain, assert that the Ming dynasty had unquestioned sovereignty over Tibet, pointing to the Ming court's issuing of various titles to Tibetan leaders, Tibetans' full acceptance of these titles, and a renewal process for successors of these titles that involved traveling to the Ming capital. Scholars within China also argue that Tibet has been an integral part of China since the 13th century and that it was thus a part of the Ming Empire. But most scholars outside China, such as Turrell V. Wylie, Melvin C. Goldstein, and Helmut Hoffman, say that the relationship was one of suzerainty, that Ming titles were only nominal, that Tibet remained an independent region outside Ming control, and that it simply paid tribute until the Jiajing Emperor (1521–1566), who ceased relations with Tibet.