Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
thanh di » thanh doi, thanh de, thanh do
hanh de » hanh ve, hanh kem
tuc gia » tac gia, duc gia, toc gia
cam tuc » cam xuc, cam tu, nam thuc
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
tang ma » mang may, tang van
ma hoi » mai hoi, xa hoi, ma hoa
va cam » va cham, va cac, va cao
v tang » 6 tang, 7 tang, 5 tang

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) or (doc sach)) v tang ma hoi. hieu va cam tuc gia ((thanh di) or (hanh de)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) v tang ma hoi. hieu va cam tuc gia ((thanh di) OR (hanh de)) cua tre.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) v tang ma hoi. hieu va cam tuc gia ((thanh di) or (hanh de)) cua tre*.