Perhaps you should try some spelling variations:
trinh chuan » trinh han, trinh quan, trinh luan
tranh chua » tranh cua, tranh chap, trinh chu
cong thanh » dong thanh, cong trinh, cong tan
hieu lang » chieu sang, hieu quang, nhieu tang
cong hach » cong sach, cong khanh, trong hach
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.

• Performing a fuzzy search may retrieve terms with similar spellings: ho hieu lang - canh ((tranh chua) or (trinh chuan)) dong ((cong hach) OR (cong thanh)) toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ho hieu lang - canh ((tranh chua) OR (trinh chuan)) dong ((cong hach) OR (cong thanh)) toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho hieu lang - canh ((tranh chua) or (trinh chuan)) dong ((cong hach) OR (cong thanh)) toan cau".
• Adding a wildcard symbol may retrieve word variants: ho hieu lang - canh ((tranh chua) or (trinh chuan)) dong ((cong hach) OR (cong thanh)) toan cau*.