Perhaps you should try some spelling variations:
thanh vai » thanh hai, thanh van, thanh tai
hieu van » thien van, lieu va, hieu ve
duoc ban » duc ban, buoc ban, duoc bat
quoc ban » quoc bao, quoc lan, quoc quan
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
vai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet

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 xa hoi. ((hieu van) OR (hieu va)) lam ((duoc ban) or (quoc ban)) thanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang xa hoi. ((hieu van) OR (hieu va)) lam ((duoc ban) OR (quoc ban)) thanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang xa hoi. ((hieu van) OR (hieu va)) lam ((duoc ban) or (quoc ban)) thanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang xa hoi. ((hieu van) OR (hieu va)) lam ((duoc ban) or (quoc ban)) thanh vai cua tre*.