Perhaps you should try some spelling variations:
thanh dai » thanh tai, thanh dat, thanh oai
thanh hai » thanh phan, thanh hoa, thanh san
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
cam duc » cao duc, pham duc, nam duoc
hieu ve » hieu va, hieu van
may hoi » may thoi, tay hoi, mai hoi
ky mang » ky nang, ke mang, ky dang

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