Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh dai » hanh tai, hanh dao, vanh dai
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va, hieu van
ve pham » vi pham, v pham, ve phan
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
v nang » va nang, vu nang, van nang
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: ((te sach) or (toc sach)) v nang ma hoi. hieu ve pham duc va hanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) v nang ma hoi. hieu ve pham duc va hanh dai cua tre.
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) v nang ma hoi. hieu ve pham duc va hanh dai cua tre*.