Perhaps you should try some spelling variations:
thanh va » thanh van, hanh va, thanh ha
thanh ve » hanh ve, thanh vien, thanh van
su sach » so sach, vu sach
cao vuc » cao duc, cao suc, cao vu
vuc van » duc van, luc van, thuc van
su tien » su kien, su hien, tu tieng
sach vu » sach va, sach tu, sach uu
hieu va » lieu va, hieu qua
vu nang » vuc nang, va nang, vu dang
va cao » va cac, va co, va dao
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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

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