Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hanh vai » hanh vi, hanh va, hanh tai
sach thi » sach thu, sach tai, sach thieu
ve triet » va trien, su triet
thi hanh » thi thanh
hieu va » lieu va, hieu qua
cac toc » cac toi, cac nuoc, cac thoi
va hanh » van hanh, va thanh, ban hanh
ca hoi » cua hoi, xa hoi, co hoi
vai ve » va ve, dai ve, vai va
cac tu » cac thu, cach tu, cac du

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach thi hanh ((ca hoi) or (cau hoi)). hieu va ((cac tu) or (cac toc)) va hanh vai ve triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach thi hanh ((ca hoi) OR (cau hoi)). hieu va ((cac tu) OR (cac toc)) va hanh vai ve triet.
• Adding a wildcard symbol may retrieve word variants: doc sach thi hanh ((ca hoi) or (cau hoi)). hieu va ((cac tu) or (cac toc)) va hanh vai ve triet*.