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 toc » cac toi, cac thoi
hieu va » lieu va, hieu qua
va viet » hoa viet, san viet, mai viet
ca hoi » cau hoi, cua hoi, co hoi
tai va » thai va, mai va, tri 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 toc) or (cac nuoc)) xa hanh tai va 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 toc) OR (cac nuoc)) xa hanh tai va viet.
• Adding a wildcard symbol may retrieve word variants: toc sach thi hanh ((ca hoi) or (xa hoi)). hieu va ((cac toc) or (cac nuoc)) xa hanh tai va viet*.