Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
thanh vi » hanh vi, thanh va, thanh ve
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
sai ky » sac ky
va bao » va bai
vi cua » vai cua, di cua
ve bac » ve bao, ve cac, ve ban
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 ((sach ky) or (sai ky)) nang o hoi. hieu ((ve bac) or (va bao)) vo van thanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sai ky)) nang o hoi. hieu ((ve bac) OR (va bao)) vo van thanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sai ky)) nang o hoi. hieu ((ve bac) or (va bao)) vo van thanh vi cua tre*.