Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
than tai » thanh tai, toan tai, nhan tai
hieu va » lieu va, hieu qua
han tai » hang tai, nhan tai, van tai
sach ly » sach y, sach lo, sach ty
cac toc » cac toi, cac nuoc, cac thoi
hieu ve » hieu van
hang xa » hoang xa, hang va, hang ca
ly hang » ly quang
cua tre » cua te, cuu tre, cua triet
toc va » hoc va, toc ta, tuc va

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ly hang xa hoi. ((hieu ve) OR (hieu va)) cac toc va ((han tai) or (than tai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ly hang xa hoi. ((hieu ve) OR (hieu va)) cac toc va ((han tai) OR (than tai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ly hang xa hoi. ((hieu ve) OR (hieu va)) cac toc va ((han tai) or (than tai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: hoc sach ly hang xa hoi. ((hieu ve) OR (hieu va)) cac toc va ((han tai) or (than tai)) cua tre*.