/images/1041385860215607387/1269888136234663957/luan-ve-phuong-phap-cua-do-nam-phu-huu-hieu-nhat-chuong-17-c17-chuong-17.txt?ex=66b1b2fd&is=66b0617d&hm=4b5e448c5aac4ebbc9e02fa4a29974ec0367e0217ec3257e2f90f81fd6360ccb&