Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, va tinh
thanh vi » hanh vi, thanh va, thanh ve
sach tu » sach thu, cach tu, sach ty
van cam » van lam, van cau, van dam
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
nang o » nang co, nang ho, nang ro
vi cua » vai cua, di cua
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: su ((sach tu) or (sac ky)) nang o hoi. thien ((van cam) OR (van nam)) duc va thanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach tu) OR (sac ky)) nang o hoi. thien ((van cam) OR (van nam)) duc va thanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach tu) or (sac ky)) nang o hoi. thien ((van cam) OR (van nam)) duc va thanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach tu) or (sac ky)) nang o hoi. thien ((van cam) OR (van nam)) duc va thanh vi cua tre*.