Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh vai » hanh vi, hanh va, hanh tai
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
va trien » va truyen, va thiet, va tuyen
hieu va » lieu va, hieu qua
cac toc » cac toi, cac thoi
xa hanh » xa thanh, xa khanh, va hanh
vai va » mai va, dai va, hai 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) OR (thi thanh)) xa hoi. hieu va ((cac nuoc) or (cac toc)) xa hanh vai va trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((thi hanh) OR (thi thanh)) xa hoi. hieu va ((cac nuoc) OR (cac toc)) xa hanh vai va trien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((thi hanh) OR (thi thanh)) xa hoi. hieu va ((cac nuoc) or (cac toc)) xa hanh vai va trien".
• Adding a wildcard symbol may retrieve word variants: toc sach ((thi hanh) OR (thi thanh)) xa hoi. hieu va ((cac nuoc) or (cac toc)) xa hanh vai va trien*.