As many as 390,000 ethnic Chinese, two-thirds of those with rightful claims to Indonesian citizenship renounced their Chinese status when the treaty came into effect in 1962. On the other hand, an estimated 60,000 ethnic Chinese students left for the People's Republic of China in the 1950s and early 1960s. The first wave of students were almost entirely educated in Chinese-language schools, but were not able to find opportunities for tertiary education in Indonesia. Seeking quality scientific professions, they entered China with high hopes for their future and that of the mainland. Subsequent migrations occurred in 1960 as part of a repatriation program and in 1965–1966 following a series of anti-communist violence that also drew anger toward the ethnic Chinese. As many as 80 percent of the original students who entered the mainland eventually became refugees in Hong Kong. During China's Cultural Revolution (1966–1976), Red Guards questioned the loyalty of the returned overseas Chinese because of their foreign connections. They were attacked as "imperialists", "capitalists", "spies", "half-breeds", and "foreign devils".As most had grown up in an urban environment they were sent to the countryside, told to "rebel against their own class background", and eventually lost contact with their families. In 1959, following the introduction of soft-authoritarian rule through Guided Democracy, the Indonesian government and military began placing restrictions on alien residence and trade. These regulations culminated in the enactment of Presidential Regulation 10 in November 1959, banning retail services by non-indigenous persons in rural areas. Ethnic Chinese, Arab, and Dutch businessmen were specifically targeted during its enforcement to provide a more favorable market for indigenous businesses. This move was met with protests from the Chinese government and some circles of Indonesian society. Javanese writer Pramoedya Ananta Toer later criticized the policies in his 1961 book "Hoakiau di Indonesia". An integrationist movement, led by the Chinese-Indonesian organisation Baperki (""), began to gather interest in 1963, including that of President Sukarno. However, a series of attacks on ethnic Chinese communities in West Java in May proved it to be short-lived, despite the government's condemnation of the violence. When Baperki was branded a communist organization in 1965 the ethnic Chinese were implicated by association; this was exacerbated in the public mind by the People's Republic of China's communism. As many as 500,000 people, the majority of them Javanese Abangan Muslims and Balinese Indonesians but including a minority of several thousand ethnic Chinese, were killed in the anti-communist purge which followed the failed coup d'état, suspected as being communist-led, on 30 September 1965.