Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach thu » sach thue, sach thieu, sach tham
thu nong » thu cong, tu nong, phu nong
dinh cuu » dinh chi
nong xa » song xa, dong xa, nong va
hieu va » hieu qua
va hang » van hang, va nang, va lang
cam tu » cam thu, nam tu, dam tu
di cuu » di cau, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach thu nong xa hoi. ((hieu va) OR (lieu va)) cam tu va hang ((di cuu) or (dinh cuu)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach thu nong xa hoi. ((hieu va) OR (lieu va)) cam tu va hang ((di cuu) OR (dinh cuu)) tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach thu nong xa hoi. ((hieu va) OR (lieu va)) cam tu va hang ((di cuu) or (dinh cuu)) tre*".