Perhaps you should try some spelling variations:
vu khanh » vu thanh, van khanh, duy khanh
vu sach » vu bach, su sach, vu khach
va hanh » van hanh, va thanh, va danh
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
va cam » va cham, va cac, va cao
cam tu » cam thu, nam tu, dam tu
vi cua » vai cua, di cua
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, o hai, o hoa

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 (vu khanh)) ky nang ((o hoi) OR (o hoc)). hieu va cam tu va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu sach) OR (vu khanh)) ky nang ((o hoi) OR (o hoc)). hieu va cam tu va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((vu sach) or (vu khanh)) ky nang ((o hoi) OR (o hoc)). hieu va cam tu va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((vu sach) or (vu khanh)) ky nang ((o hoi) OR (o hoc)). hieu va cam tu va hanh vi cua tre*.