Can Vietnam's new president end months of turmoil? / Can Vietnam's new president check the power of its party chief? / Vietnam's president is confirmed as the new Communist Party chief / Vietnam succession in focus as president stands in for party chief / Beware of Vietnam's new authoritarian president / Vietnam's president resigns in latest twist of anti-graft campaign shaking its fast-growing economy / Why has Vietnam's president resigned after just a year? / Vietnam president's downfall stokes political turmoil fears