Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
sach thu » sach thue, sach thieu, sach tham
cam dua » ca dua, cay dua, chay dua
san cua » sang cua, ban cua, dan cua
dua ban » dia ban, cua ban, qua ban
hieu va » hieu qua
sach ty » sach y, sach tu, xach tay
nang xa » nang x, lang xa, nang ma
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 ty) or (sach thu)) nang xa hoi. ((hieu va) OR (lieu va)) cam dua ban thanh san cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach thu)) nang xa hoi. ((hieu va) OR (lieu va)) cam dua ban thanh san cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) or (sach thu)) nang xa hoi. ((hieu va) OR (lieu va)) cam dua ban thanh san cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) or (sach thu)) nang xa hoi. ((hieu va) OR (lieu va)) cam dua ban thanh san cua tre*.