Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
hai cua » thai cua, dai cua, hoi cua
dau hai » dai hai, dau ha, cau hai
cam tuc » cam xuc, nam thuc, dam thuc
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
ky danh » ky anh, ky dang
ky lang » ky nang, ky dang, ky tang
cam tu » cam thu, nam tu, dam tu
va dau » va dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((ky lang) or (ky danh)) xa hoi. hieu ve ((cam tuc) or (cam tu)) va dau hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky danh)) xa hoi. hieu ve ((cam tuc) OR (cam tu)) va dau hai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) or (ky danh)) xa hoi. hieu ve ((cam tuc) or (cam tu)) va dau hai cua tre*.