Perhaps you should try some spelling variations:
trinh viet » ninh viet, trinh vat
thong cong » trong cong, tong cong, thong thong
hieu tach » hieu cach, chiet tach, chieu sach
trinh vit » trinh vat, trinh vuot, trinh van
doc hieu » toc thieu, hoc thieu, hoc hien
trinh vi » trinh va, trinh ve, trinh van
cong tai » cong thai, cong tac, dong tai
tai phan » tai thanh, tai phong, tai ngan

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 tach - canh ((trinh vi) or (((trinh vit) OR (trinh viet)))) thong cong tai phan tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu tach - canh ((trinh vi) OR (((trinh vit) OR (trinh viet)))) thong cong tai phan tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu tach - canh ((trinh vi) or (((trinh vit) OR (trinh viet)))) thong cong tai phan tu".
• Adding a wildcard symbol may retrieve word variants: doc hieu tach - canh ((trinh vi) or (((trinh vit) OR (trinh viet)))) thong cong tai phan tu*.