Perhaps you should try some spelling variations:
vu sach » vu bach, su sach, vu khach
hieu va » lieu va, hieu qua
cam thu » nam thu, cac thu, ca thu
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
co hoi » co hoc
va cam » va cham, va cac, va cao
thu va » thuc va, thue va, tu va
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: ((vu sach) or (vay khach)) ky nang ((co loi) OR (co hoi)). hieu va cam thu va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu sach) OR (vay khach)) ky nang ((co loi) OR (co hoi)). hieu va cam thu va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((vu sach) or (vay khach)) ky nang ((co loi) OR (co hoi)). hieu va cam thu va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((vu sach) or (vay khach)) ky nang ((co loi) OR (co hoi)). hieu va cam thu va hanh vi cua tre*.