Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
sach ky » sac ky, sach y, sach ty
lai cua » dai cua, hai cua, lai chau
dau lai » dao lai, dat lai, dau hai
cac tao » cau tao, cac tac, cac tai
hieu va » lieu va, hieu qua
hieu ve » hieu van
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
cua tre » cua te, cuu tre, cua triet
va dau » va dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky tang ma hoa. ((hieu ve) or (hieu va)) ((cac tao) OR (cac tro)) va dau lai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky tang ma hoa. ((hieu ve) OR (hieu va)) ((cac tao) OR (cac tro)) va dau lai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky tang ma hoa. ((hieu ve) or (hieu va)) ((cac tao) OR (cac tro)) va dau lai cua tre*".