Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
dao nang » cao nang, da nang, dai nang
thuc ban » thuoc ban, thuc dan, thu ban
sach dao » lanh dao
hang di » hang doi, hang vi, hang dien
hanh di » hanh vi, hanh de, danh di
su sach » so sach, vu sach
mai hoi » mai khoi, dai hoi, lai hoi

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

• If you are trying to use Boolean operators, they must be ALL CAPS: su sach dao nang ((xa hoi) OR (mai hoi)). hieu van nam thuc ban ((hanh di) OR (hang di)) cua vat~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach dao nang ((xa hoi) or (mai hoi)). hieu van nam thuc ban ((hanh di) OR (hang di)) cua vat~".
• Adding a wildcard symbol may retrieve word variants: su sach dao nang ((xa hoi) or (mai hoi)). hieu van nam thuc ban ((hanh di) OR (hang di)) cua vat*.