Malaysia-based Yazhou Zhoukan conducted an interview with former researcher at the China Seismological Bureau Geng Qingguo (耿庆国), in which Geng claimed that a confidential written report was sent to the State Seismological Bureau on April 30, 2008, warning about the possible occurrence of a significant earthquake in Ngawa Prefecture region of Sichuan around May 8, with a range of 10 days before or after the quake. Geng, while acknowledging that earthquake prediction was broadly considered problematic by the scientific community, believed that "the bigger the earthquake, the easier it is to predict." Geng had long attempted to establish a correlation between the occurrence of droughts and earthquakes; Premier Zhou Enlai reportedly took an interest in Geng's work. Geng's drought-earthquake correlation theory was first released in 1972, and said to have successfully predicted the 1975 Haicheng and 1976 Tangshan earthquakes. The same Yazhou Zhoukan article pointed out the inherent difficulties associated with predicting earthquakes. In response, an official with the Seismological Bureau stated that "earthquake prediction is widely acknowledged around the world to be difficult from a scientific standpoint." The official also denied that the Seismological Bureau had received reports predicting the earthquake.