Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
ban thanh » ban hanh, ban hang
may thoi » gay thoi, may thi, tay thoi
su sach » so sach, vu sach
cam duc » cam xuc, cao duc, nam duoc
hieu ve » hieu va, hieu van
may hoi » tay hoi, mai hoi, may hmi
sach ky » sac ky, sach y, sach ty
ky mang » ky nang, ke mang, ky dang
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky mang ((may hoi) or (may thoi)). hieu ve ((cam duc) OR (pham duc)) ban thanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky mang ((may hoi) OR (may thoi)). hieu ve ((cam duc) OR (pham duc)) ban thanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky mang ((may hoi) or (may thoi)). hieu ve ((cam duc) OR (pham duc)) ban thanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky mang ((may hoi) or (may thoi)). hieu ve ((cam duc) OR (pham duc)) ban thanh dai cua tre*.