Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
danh sai » dung sai, danh bat, danh dau
su sach » so sach, vu sach
ky dang » ky danh
hieu ve » hieu va
va danh » va dinh, va dan, va hanh
sai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet

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 ((ky nang) or (ky dang)) xa hoi. ((hieu ve) OR (hieu van)) cac nuoc va danh sai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ky nang) OR (ky dang)) xa hoi. ((hieu ve) OR (hieu van)) cac nuoc va danh sai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ky nang) or (ky dang)) xa hoi. ((hieu ve) OR (hieu van)) cac nuoc va danh sai cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((ky nang) or (ky dang)) xa hoi. ((hieu ve) OR (hieu van)) cac nuoc va danh sai cua tre*.