Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, hang cong
trung cua » truong cua, trung tuan, dung cua
trung cap » truong cao, trung tam
hieu cac » hieu va, hieu van, vien cac
hieu luc » hieu luat, hieu qua
cong dan » cong san, cong tan, huong dan
dan toan » van toan, dan than, manh toan
toan cao » toan ban, toan tap

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((hieu cac) OR (hieu luc)) - hanh ((trung cua) or (trung cap)) nhung cong dan toan cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu cac) OR (hieu luc)) - hanh ((trung cua) OR (trung cap)) nhung cong dan toan cao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu cac) OR (hieu luc)) - hanh ((trung cua) or (trung cap)) nhung cong dan toan cao".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu cac) OR (hieu luc)) - hanh ((trung cua) or (trung cap)) nhung cong dan toan cao*.