Perhaps you should try some spelling variations:
trung tuan » trung thanh, trung tam, tran tuan
thong cong » trong cong, tong cong, thong thong
hieu quan » hieu qua, lieu quan, thien quan
trung cua » truong cua, trung cap, dung cua
dan toan » van toan, dan than, manh toan
toan cau » toan cao, toan ban, toan tap
ho hieu » ho chieu, hoi hieu, nho hieu

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ho hieu quan - hanh ((trung cua) OR (trung tuan)) ((thong cong) OR (han tong)) dan toan cau~.
• Adding a wildcard symbol may retrieve word variants: ho hieu quan - hanh ((trung cua) or (trung tuan)) ((thong cong) or (han tong)) dan toan cau*.