National Basketball Association (NBA) wants to double the National Basketball Association's Chinese operations over the next two years, The Associated Press reported, citing commissioner David Stern.   NBA’s branded products and broadcast rights in the country have been growing at 30 per cent a year.   "The China market is our most important and largest market outside the United States," Stern told the Associated Press in Guangzhou.   The league currently has three offices in China, including Hong Kong, with about 50 staff. "My guess is we'll double it in size by the Beijing Olympics" in 2008, Stern said.   His plan is to boost marketing partners, sell more league products and have a greater online presence, according to the AP.