Catastrophic health expenditure of Vietnamese patients with gallstone diseases – a case for health insurance policy revaluation oleh Tran BX, Tran TD, Nathan N, Ngo CQ, Nguyen LT, Nguyen LH, Nguyen HLT, Nguyen CT, Do HP, Nguyen THT, Tran TT, Thai TPT, Dang AK, Nguyen NB, Latkin CA, Ho CSH, Ho RCM