Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van pham » san pham, van phan, van phat
hanh lai » hanh lam, hanh tai, thanh lap
cua viet » ca viet, hoa viet, cua vat
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
va hanh » van hanh, va thanh, va danh
lai cua » dai cua, hai cua, lai chau
x hoi » xa hoi, o hoi, x ho
o hai » co hai, so hai, o lai

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 nang ((x hoi) or (o hai)). hieu van pham duc va hanh lai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((x hoi) OR (o hai)). hieu van pham duc va hanh lai cua viet.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((x hoi) or (o hai)). hieu van pham duc va hanh lai cua viet*.