Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, va tinh
hieu van » hieu va, thien van, lieu va
thanh va » thanh van, hanh va, thanh ha
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
van cau » van dau, van hau, van chat
truc va » thuc va, thuc vat, trung va
cua tre » cua te, cuu tre, cua triet
x hoi » xa hoi, o hoi, 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 ky nang ((x hoi) OR (x ho)). hieu van cau truc va thanh va ((cua tre) or (cua vat))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((x hoi) OR (x ho)). hieu van cau truc va thanh va ((cua tre) OR (cua vat)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((x hoi) OR (x ho)). hieu van cau truc va thanh va ((cua tre) or (cua vat))".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((x hoi) OR (x ho)). hieu van cau truc va thanh va ((cua tre) or (cua vat))*.