Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, cam thu
vat hanh » vat thanh, van hanh, va hanh
ban hanh » ban hang
su sach » so sach, vu sach
van cam » van nam, van lam, van cau
doi cua » dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
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.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach y nang o hoi. hieu van cam thuc ((vat hanh) or (ban hanh)) doi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y nang o hoi. hieu van cam thuc ((vat hanh) OR (ban hanh)) doi cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach y nang o hoi. hieu van cam thuc ((vat hanh) or (ban hanh)) doi cua tre*.