P. Christiaan Klieger, an anthropologist and scholar of the California Academy of Sciences in San Francisco, writes that the vice royalty of the Sakya regime installed by the Mongols established a patron and priest relationship between Tibetans and Mongol converts to Tibetan Buddhism. According to him, the Tibetan lamas and Mongol khans upheld a "mutual role of religious prelate and secular patron," respectively. He adds that "Although agreements were made between Tibetan leaders and Mongol khans, Ming and Qing emperors, it was <answer>the Republic of China and its Communist successors</answer> that assumed the former imperial tributaries and subject states as integral parts of the Chinese nation-state."
Who does P. Christiaan Klieger believe undertook the former imperial tributaries?
the Republic of China and its Communist successors