Perhaps you should try some spelling variations:
dung tren » dung trong, dung trung
hieu va » lieu va, hieu qua
duc tre » duoc tren, duc tien
han tai » hang tai, nhan tai, van tai
sach ly » sach y, sach lo, sach ty
co sach » bo sach, cuon sach, hoc sach
hieu ve » hieu van
hang xa » hoang xa, hang va, hang ca
ly hang » ly quang
cac toc » cac toi, cac nuoc, cac thoi
toc va » hoc va, toc ta, tuc va
va han » va phan, van han, va hanh

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

• Performing a fuzzy search may retrieve terms with similar spellings: co sach ly hang xa hoi. ((hieu ve) or (hieu va)) cac toc va han tai ((duc tre) or (dung tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach ly hang xa hoi. ((hieu ve) OR (hieu va)) cac toc va han tai ((duc tre) OR (dung tren)).
• Adding a wildcard symbol may retrieve word variants: co sach ly hang xa hoi. ((hieu ve) or (hieu va)) cac toc va han tai ((duc tre) or (dung tren))*.