premise: In 2006, China and Russia have made "historic breakthroughs" in investment and cooperation in the petroleum industry, Zhou Jiping, deputy general manager of the China National Petroleum Corporation (CNPC), said in Beijing on Thursday.
  So far this year, the two countries have signed a series of agreements on setting up two joint venture companies involving oil and gas exploitation and the construction of a pipeline transporting Russian crude oil to the Chinese border, according to the CNPC official.
  Leaders of Chinese and Russian oil companies attending the on-going third meeting for promoting investment in China and Russia were optimistic about the prospects of the two countries' cooperation in the oil sector.
  Zhou said that Sino-Russian cooperation in the oil industry will help stabilize both the regional and global oil markets.
  Sergei Bogdanchikov, president of Russian oil giant Rosneft, said China is a stable and rapidly-growing market for Russian oil. He pledged to go all out to promote cooperation in oil industry.
   Why was the third meeting called for leaders of Chinese and Russian oil companies?
hypothesis: promoting investment in China and Russia