Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh dai » hanh tai, hanh dao, vanh dai
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
xa hanh » xa thanh, xa khanh, va hanh
cac tuc » cac tu, cac tac, cac nuoc
ca hoi » cau hoi, cua hoi, co hoi
dai ve » dap ve, dau ve, dai va

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach thi hanh ((ca hoi) OR (xa hoi)). hieu va ((cac tuc) or (cac toc)) xa hanh dai ve triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach thi hanh ((ca hoi) OR (xa hoi)). hieu va ((cac tuc) OR (cac toc)) xa hanh dai ve triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach thi hanh ((ca hoi) OR (xa hoi)). hieu va ((cac tuc) or (cac toc)) xa hanh dai ve triet".
• Adding a wildcard symbol may retrieve word variants: toc sach thi hanh ((ca hoi) OR (xa hoi)). hieu va ((cac tuc) or (cac toc)) xa hanh dai ve triet*.