Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
danh dai » danh dau, danh di, danh sai
hieu va » lieu va, hieu qua
cua tre » cua te, cua triet, dua tren
va danh » va dinh, va dan, va hanh
va pham » van pham, va phat, va phap
sang ma » tang ma, nang ma, sang tao
ky sang » ky nang, ky dang, ky tang
cuu tre » cau tren, cau treo
ma hoi » mai hoi, xa hoi, ma hoa

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

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