Perhaps you should try some spelling variations:
trinh thiet » trinh viet, trinh thi
trinh thuat » trinh luat, trinh thuc, trinh chat
hien xanh » hien hanh, hien nhanh, chieu xanh
hang cong » dang cong, hang nong, bang cong
chinh cau » chinh chau, chinh ca, chinh tai
chinh can » chinh ca, chinh ban, chinh ngan
cong dan » cong san, cong tan, huong dan

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

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