Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
thanh de » hanh de, thanh ve, thanh do
doc sach » hoc sach, nuoc sach, dac sac
thanh di » thanh doi, thanh do, thanh dinh
xuc gia » duc gia, luc gia, tuc gia
hieu va » lieu va, hieu qua
tang ma » mang may, tang van
cua tre » cua te, cuu tre, cua triet
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 xuc gia ((thanh di) or (thanh 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 xuc gia ((thanh di) OR (thanh de)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) v tang ma hoi. hieu va cam xuc gia ((thanh di) or (thanh de)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) v tang ma hoi. hieu va cam xuc gia ((thanh di) or (thanh de)) cua tre*.