Perhaps you should try some spelling variations:
cam thuc » am thuc, nam thuc, can thuc
hieu ve » hieu va, hieu van
cam thu » nam thu, cac thu, ca thu
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua
o hoi » co hoi, o hai, o hoa
o hoc » co hoc, mo hoc, so hoc

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

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