Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu cac » hieu va, hieu van, vien cac
hieu luc » hieu luat, hieu qua
nang ma » tang ma, sang ma, nang cao
sach ky » sac ky, sach y, sach ty
va tinh » may tinh
dai cuu » dai cua, dai huu
cuu tre » cua tre, cau tren, cau treo
ma hoi » mai hoi, xa hoi, ma hoa
va dan » ca dan, va dao, va dau

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 nang ma hoi. ((hieu cac) or (hieu luc)) cau truc ((va tinh) or (va dan)) dai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ma hoi. ((hieu cac) OR (hieu luc)) cau truc ((va tinh) OR (va dan)) dai cuu tre.
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ma hoi. ((hieu cac) or (hieu luc)) cau truc ((va tinh) or (va dan)) dai cuu tre*.