Perhaps you should try some spelling variations:
thu sac » thu sach, thu san, thu xac
qua cac » cua cac
cau hai » cau hoi, cau hat, cau ha
hai cua » thai cua, dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
va cau » van cau, va cac, va dau
x hoi » xa hoi, o hoi, x ho
du va » dau va, tu va, su va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sac ky nang x hoi. hieu qua cac du va cau hai cua tre~.
• Adding a wildcard symbol may retrieve word variants: thu sac ky nang x hoi. hieu qua cac du va cau hai cua tre*.