China Daily newspaper quoted Nanjing University sociology professor Zhu Li saying Zheng's attack inspired copycats.

CNN: Schools in China prepare for copycat attacks

In addition to income measurement, a research team led by Professor Zhou Xiaohong in Nanjing University further defined middle class occupations as professionals in management and technology, entrepreneurs, private business owners, and civil servants (meaning government officials).

FORBES: Defining the Chinese Middle Class

But researchers at Nanjing Agricultural University found that 10% of China's rice crop is contaminated with the metal.

WSJ: Review & Outlook: China's Toxic Rice Bowl

According to 2011 research by Nanjing Agricultural University, roughly 10% of all rice sold in China is tainted by cadmium.

WSJ: Cadmium-Tainted Rice Found in Guangzhou

Based on a survey conducted in 2007 and 2008, researchers at Nanjing Agricultural University estimated that roughly 10% of the country's rice supplies contained excessive levels of the poisonous metal.

WSJ: China Seeks to Calm Anxiety Over Rice

According to 2011 research at Nanjing Agricultural University, roughly 10% of all rice sold in China is tainted by cadmium, the result of use of industrial wastewater for irrigation, dumping of industrial waste and overapplication of fertilizer.

WSJ: Cadmium-Tainted Rice Found in Guangzhou

Foreign firms should establish long-term interaction with leading Chinese faculty at Chinese universities, from top-rated Beijing University to Tsinghua to Fudan (in Shanghai) to other colleges in Tianjin, Dalian, Nanjing, Wuhan, Xiamen and Guangdong.

FORBES: China Turns Its Focus To Africa