Perhaps you should try some spelling variations:
hieu nganh » vien nganh, hiem ngan, hieu manh
hieu xanh » chieu xanh, hieu manh, dieu hanh
trinh han » trinh quan
tong cong » trong cong, cong cong, dung cong
trinh ha » trinh hoa, trinh nha, trinh he
cong dan » cong san, cong tan, huong dan
dan than » dan chan, ban than, van than
than cau » toan cau, phan cau, than cap

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc ((hieu xanh) or (hieu nganh)) - hanh ((trinh ha) OR (trinh han)) tong cong dan than cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu xanh) OR (hieu nganh)) - hanh ((trinh ha) OR (trinh han)) tong cong dan than cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu xanh) or (hieu nganh)) - hanh ((trinh ha) OR (trinh han)) tong cong dan than cau".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu xanh) or (hieu nganh)) - hanh ((trinh ha) OR (trinh han)) tong cong dan than cau*.