Perhaps you should try some spelling variations:
co sach » cuon sach, hoc sach
cao luc » bao luc, cao duc, cao suc
bo sach » hoc sach
xang xa » lang xa, mang xa, ang xa
hieu ve » hieu van
hang vi » hang va, hanh vi, hang di
va hang » van hang, va nang, va lang
hieu va » lieu va, hieu qua
vi cua » vai cua, di cua
luc va » duc va, tuc va, loc va
cua tu » cua tuc, cua su, cua cu

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((co sach) OR (bo sach)) ty xang xa hoi. ((hieu ve) or (hieu va)) cao luc va hang vi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((co sach) OR (bo sach)) ty xang xa hoi. ((hieu ve) OR (hieu va)) cao luc va hang vi cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((co sach) OR (bo sach)) ty xang xa hoi. ((hieu ve) or (hieu va)) cao luc va hang vi cua tu".
• Adding a wildcard symbol may retrieve word variants: ((co sach) OR (bo sach)) ty xang xa hoi. ((hieu ve) or (hieu va)) cao luc va hang vi cua tu*.