Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach thi » sach thu, sach tai, sach thieu
thi hanh » thi thanh
hanh tai » thanh tai, hang tai, han tai
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
xa hanh » xa thanh, xa khanh, va hanh
cac tuc » cac toc, cac tu, cac tac
hieu va » lieu va, hieu qua
ca viet » va viet, co viet, hoa viet
ca hoi » cau hoi, cua hoi, co hoi
tai ca » tai cac, tai cao, tai cua

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 nuoc)) xa hanh tai ca viet~.
• 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 nuoc)) xa hanh tai ca viet.
• 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 nuoc)) xa hanh tai ca viet".
• Adding a wildcard symbol may retrieve word variants: toc sach thi hanh ((ca hoi) OR (xa hoi)). hieu va ((cac tuc) or (cac nuoc)) xa hanh tai ca viet*.