Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
dang xay » dang van, van xay
hieu van » hieu va, thien van, lieu va
nang xa » nang x, lang xa, nang ma
sach ty » sach y, sach tu, sach thu
van cac » van hac, van cau, van bac
cac xuc » cam xuc, cac nuoc, chat xuc
su tien » su kien, su hien, tu tieng
xuc va » duc va, tuc va, luc va

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ty ((nang xa) or (dang xay)) hoi. hieu van cac xuc va ((danh gia) OR (dan gian)) su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ty ((nang xa) OR (dang xay)) hoi. hieu van cac xuc va ((danh gia) OR (dan gian)) su tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ty ((nang xa) or (dang xay)) hoi. hieu van cac xuc va ((danh gia) OR (dan gian)) su tien".
• Adding a wildcard symbol may retrieve word variants: doc sach ty ((nang xa) or (dang xay)) hoi. hieu van cac xuc va ((danh gia) OR (dan gian)) su tien*.