Perhaps you should try some spelling variations:
thong cong » trong cong, tong cong, thong thong
hieu manh » chieu xanh, hieu nganh, dieu hanh
trinh thi » trinh tai, dinh thi, trinh tu
doc hieu » toc thieu, hoc thieu, hoc hien
trinh he » trinh han, trinh hoa, trinh ky
dan toan » van toan, manh toan, xuan toan
dan than » dan chan, ban than, van than

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: doc hieu manh - hanh ((trinh he) OR (trinh thi)) thong cong ((dan toan) OR (dan than)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu manh - hanh ((trinh he) or (trinh thi)) thong cong ((dan toan) OR (dan than)) cau~".
• Adding a wildcard symbol may retrieve word variants: doc hieu manh - hanh ((trinh he) or (trinh thi)) thong cong ((dan toan) OR (dan than)) cau*.