The availability of sources has repeatedly shaped the academic study of contemporary China. In the 1950s and early 1960s scholars relied heavily on official Chinese government sources, which were often accessed through U.S. government translation series. By the mid-1960s, researchers began to draw upon a broader range of Chinese media, especially from the provincial and local levels, as well as interviews with refugees and legal immigrants conducted at the Union Research Institute and Universities Service Centre in Hong Kong. Access to Cultural Revolution materials in the 1970s, particularly revealing Red Guard newspapers and unauthorized collections of Communist Party documents and Politburo member speeches, added an additional level of understanding. The opening of China to fieldwork in 1979 prompted research programmes such as Zouping county, while the use of mainland libraries and archives provided access to an even wider range of materials. Since the late 1980s, as mainland researchers began to examine their society and its recent past, Chinese scholarly writings have offered a new level of detail and rigour that was previously unavailable.