Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
hanh vai » hanh vi, hanh va, hanh tai
tu sach » su sach, te sach, tu cach
vai cua » dai cua, hai cua, lai cua
va hanh » van hanh, va thanh, va danh
cac toi » cac thoi
cac loc » cac lop, cac toc, cac hoc
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
sang ma » tang ma, nang ma, sang tao
ky sang » ky nang, ky dang, ky tang
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (thu sach)) ky sang ma hoi. hieu ve ((cac loc) or (cac toi)) va hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky sang ma hoi. hieu ve ((cac loc) OR (cac toi)) va hanh vai cua tre.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky sang ma hoi. hieu ve ((cac loc) or (cac toi)) va hanh vai cua tre*.