Perhaps you should try some spelling variations:
vat hanh » vat thanh, van hanh, va hanh
nam thuc » nam thuoc, am thuc, nam thu
so sach » so sanh, bo sach, co sach
hanh di » hanh vi, hanh de, hang di
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
vu sach » vu bach, su sach, vu khach
va nam » van nam, ha nam, va nay
y nang » ky nang, ly nang, v nang
di cua » dai cua, doi cua, de cua
x hoi » xa hoi, o hoi, x ho
o hoc » co hoc, mo hoc, so hoc

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

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