Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
cham duc » pham duc, cham soc, pham duy
tu cach » tu cac
duc van » duc va, duc tan, duc manh
vu cham » va cham, vu kham, tu cham
hieu vu » hieu va, hieu ve, hieu su
cua tre » cua te, cuu tre, cua triet
so sach » so sanh, bo sach, co sach
vi cua » vai cua, di cua
x hoi » xa hoi, x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu cach) or (so sach)) ky nang ((x hoi) or (o hoi)). hieu vu cham duc van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu cach) OR (so sach)) ky nang ((x hoi) OR (o hoi)). hieu vu cham duc van hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: ((tu cach) or (so sach)) ky nang ((x hoi) or (o hoi)). hieu vu cham duc van hanh vi cua tre*.