Perhaps you should try some spelling variations:
hieu xanh » chieu xanh, hieu manh, hieu nganh
cong vang » cong lang, cong quang, cong ngang
doc hieu » toc thieu, hoc thieu, hoc hien
dinh cua » dinh cuu, sinh cua, dinh cu
tinh cua » trinh cua, sinh cua, tinh chat
cong van » cong san, song van, cong tan
than tap » toan tap, han tap, phan tap

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 - hoang ((dinh cua) or (tinh cua)) nhung ((cong van) OR (cong vang)) than tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu xanh - hoang ((dinh cua) OR (tinh cua)) nhung ((cong van) OR (cong vang)) than tap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu xanh - hoang ((dinh cua) or (tinh cua)) nhung ((cong van) OR (cong vang)) than tap".
• Adding a wildcard symbol may retrieve word variants: doc hieu xanh - hoang ((dinh cua) or (tinh cua)) nhung ((cong van) OR (cong vang)) than tap*.