Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
thi hanh » thi thanh
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
sach thi » sach thu, sach tai, sach thieu
hanh vai » hanh vi, hanh va, hanh tai
va triet » va trien, ve triet, cua triet
hanh ca » hanh cac, hanh cat, hanh cua
hieu va » lieu va, hieu qua
cac toc » cac toi, cac thoi
xa hanh » xa thanh, xa khanh, va hanh
ca hoi » cau hoi, cua hoi, xa hoi
thiet » thieu

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