Perhaps you should try some spelling variations:
nang xa » nang x, lang xa, nang ma
va hanh » van hanh, va thanh, va danh
cac toc » cac toi, cac nuoc, cac thoi
su sach » so sach, vu sach
va nang » van nang, da nang, cam nang
so sanh » do sanh
qua cac » cua cac
toc va » hoc va, toc ta, tuc va
vi cau » va cau, di cau, viet cau
ve cau » ke cau, va cau, ve cac

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 (so sanh)) va nang xa hoi. hieu qua cac toc va hanh ((vi cau) OR (ve cau)) treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sanh)) va nang xa hoi. hieu qua cac toc va hanh ((vi cau) OR (ve cau)) treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sanh)) va nang xa hoi. hieu qua cac toc va hanh ((vi cau) OR (ve cau)) treo".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sanh)) va nang xa hoi. hieu qua cac toc va hanh ((vi cau) OR (ve cau)) treo*.