Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
hanh ki » hanh vi, hanh ky, hanh kien
xuc van » duc van, luc van, vuc van
sach vu » sach va, sach tu, sach uu
so viet » hoc viet
nang ma » tang ma, sang ma, mang may
va cao » va cac, va co, va dao
va cam » va cham, va cac, va cai
ki so » khi so, ka so, ki su

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 vu ((nang ma) OR (nang cao)) hoi. hieu ((va cam) or (va cao)) xuc van hanh ki so viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach vu ((nang ma) OR (nang cao)) hoi. hieu ((va cam) OR (va cao)) xuc van hanh ki so viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach vu ((nang ma) OR (nang cao)) hoi. hieu ((va cam) or (va cao)) xuc van hanh ki so viet".
• Adding a wildcard symbol may retrieve word variants: tu sach vu ((nang ma) OR (nang cao)) hoi. hieu ((va cam) or (va cao)) xuc van hanh ki so viet*.