Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
van hanh » van thanh, ban hanh, van anh
ky dang » ky nang, ky danh
ky tang » ky nang, kho tang, ky trong
qua cam » qua cham, qua cac, qua ca
va danh » va dinh, va dan, va hanh
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ((ky dang) or (ky tang)) ha noi. hieu qua cam xuc ((van hanh) or (va danh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ((ky dang) OR (ky tang)) ha noi. hieu qua cam xuc ((van hanh) OR (va danh)) vi cua tre.
• Adding a wildcard symbol may retrieve word variants: doc sach ((ky dang) or (ky tang)) ha noi. hieu qua cam xuc ((van hanh) or (va danh)) vi cua tre*.