Perhaps you should try some spelling variations:
hieu viec » nhieu viec, hieu ve, sieu viet
sach thu » sach thue, sach thieu, sach tham
thu nang » thi nang, thu hang, thu bang
viec can » viec ban, vien can, view can
can quoc » han quoc, dan quoc, cac quoc
cua viet » ca viet, hoa viet, cua vat
su sach » so sach, vu sach
mai hoi » mai khoi, lai hoi, mai doi
dai hoi » dai hoc, dai hai, dai moi
quoc va » nuoc va, duoc va, quoc gia
va hanh » van hanh, va thanh, va danh
vi cua » vai cua, di cua

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 thu nang ((mai hoi) or (dai hoi)). hieu viec can quoc va hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach thu nang ((mai hoi) OR (dai hoi)). hieu viec can quoc va hanh vi cua viet.
• Adding a wildcard symbol may retrieve word variants: su sach thu nang ((mai hoi) or (dai hoi)). hieu viec can quoc va hanh vi cua viet*.