Perhaps you should try some spelling variations:
dai hoi » dai hoc, dai hai, dai moi
dai hoa » dai khoa, dai hoc, day hoa
va hanh » van hanh, va thanh, va danh
hieu ve » hieu va, hieu van
su sach » so sach
vu sach » vu bach, vu khach
dam tu » nam tu, cam tu, tam tu
v nang » va nang, vu nang, van nang
ve dam » ven dam, ke dam, va dam
x hoi » xa hoi, o hoi, x ho

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) or (vu sach)) v nang x hoi. hieu ve dam tu va hanh ((dai hoa) OR (dai hoi)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (vu sach)) v nang x hoi. hieu ve dam tu va hanh ((dai hoa) OR (dai hoi)) viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (vu sach)) v nang x hoi. hieu ve dam tu va hanh ((dai hoa) OR (dai hoi)) viet".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (vu sach)) v nang x hoi. hieu ve dam tu va hanh ((dai hoa) OR (dai hoi)) viet*.