Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
sach vu » sach va, sach tu, sach uu
vu nang » vuc nang, va nang, vu dang
van cam » van nam, van lam, van cau
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
tuc va » thuc va, truc va, tuc xa
di cua » dai cua, doi cua, de 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: toc sach vu nang o hoi. hieu van cam ((tuc va) or (duc va)) hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach vu nang o hoi. hieu van cam ((tuc va) OR (duc va)) hanh di cua tre*.