Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
hieu van » hieu va, thien van, lieu va
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, dua tren
xa hanh » xa thanh, xa khanh, va hanh
cac toi » cac thoi
su sach » so sach, vu sach
cac toc » cac nuoc, cac thoi
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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

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