Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
chat xuc » chat huu, cam xuc, chao xu
xuc van » duc van, luc van, vuc van
hanh va » hang va, hanh vi
cao hoi » cau hoi, co hoi, cao hoc
hieu ve » hieu va
sach ky » sach y, sach ty, sach kem
sac ky » cac ky, sai ky
va va » va van, va vua, va vai
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sach ky) or (sac ky)) nang cao hoi. ((hieu ve) OR (hieu van)) chat xuc van hanh va va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) nang cao hoi. ((hieu ve) OR (hieu van)) chat xuc van hanh va va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sac ky)) nang cao hoi. ((hieu ve) OR (hieu van)) chat xuc van hanh va va thiet".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) nang cao hoi. ((hieu ve) OR (hieu van)) chat xuc van hanh va va thiet*.