Reuters: Chinese shares tumbled more than 8 percent on Monday as an unprecedented government rescue plan to prop up valuations abruptly ran out of steam, throwing the viability of Beijing's efforts to stave off a deeper crash into doubt. Major indexes suffered their largest one-day drop since 2007, shattering three weeks of relative calm in China's volatile stock markets since Beijing unleashed a barrage of support measures to arrest a slump that had started in mid-June...
