U.S. Treasury Secretary Janet Yellen sent a message of mutual cooperation at a meeting Sunday with Chinese Premier Li Qiang‚ highlighting the improvement in relations since her visit to China last year while recognizing that major differences remain.After focusing on trade and economic issues for the first two days of her visit‚ Yellen turned to the broader U.S.-China relationship in the meeting with Li‚ one of Chinas top leaders.While we have more to do‚ I believe that‚ over the past...