Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cac thoi » cac toi, cac hop, cac tro
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 tuc » cac toc, cac tu, cac nuoc
hanh ca » hanh cac, hanh cat, hanh cua
cac tac » cac toc, cac bac, cac dac
xa hanh » xa thanh, xa khanh, va hanh
hanh va » hang va, hanh vi
ca hoi » cau hoi, cua hoi, xa hoi
va ve » va de, va le, va vi

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