Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
va xanh » va danh, va hanh, va banh
ve pham » vi pham, v pham, ve phan
hieu ve » hieu va, hieu van
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
va anh » van anh, va danh, va hanh
di cua » dai cua, doi cua, de cua

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)) ky tang ma hoi. hieu ve pham duc ((va xanh) OR (va anh)) di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky tang ma hoi. hieu ve pham duc ((va xanh) OR (va anh)) di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ky tang ma hoi. hieu ve pham duc ((va xanh) OR (va anh)) di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky tang ma hoi. hieu ve pham duc ((va xanh) OR (va anh)) di cua tre*.