Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
xuc van » duc van, luc van, vuc van
sach vu » sach va, sach tu, sach uu
su viet » so viet
vu nang » vuc nang, va nang, vu dang
va cao » va cac, va co, va dao
ma hoi » mai hoi, ma hoa, me hoi
va cam » va cham, va cac, va cai
vi su » va su, ve su, 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 hoi) or (xa hoi)). hieu ((va cam) or (va cao)) xuc van hanh vi su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach vu nang ((ma hoi) OR (xa hoi)). hieu ((va cam) OR (va cao)) xuc van hanh vi su viet.
• Adding a wildcard symbol may retrieve word variants: tu sach vu nang ((ma hoi) or (xa hoi)). hieu ((va cam) or (va cao)) xuc van hanh vi su viet*.