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 vai » hanh vi, hanh va, hanh tai
hanh xa » hanh va, hanh ma, hanh xu
hieu va » hieu qua
cac tuc » cac tu, cac tac, cac nuoc
cac toc » cac toi, cac nuoc, cac thoi
xa hanh » xa thanh, xa khanh, va hanh
vai va » mai va, dai va, hai va
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: toc sach thi hanh xa hoi. ((hieu va) OR (lieu va)) ((cac tuc) or (cac toc)) xa hanh vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach thi hanh xa hoi. ((hieu va) OR (lieu va)) ((cac tuc) OR (cac toc)) xa hanh vai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach thi hanh xa hoi. ((hieu va) OR (lieu va)) ((cac tuc) or (cac toc)) xa hanh vai va thiet".
• Adding a wildcard symbol may retrieve word variants: toc sach thi hanh xa hoi. ((hieu va) OR (lieu va)) ((cac tuc) or (cac toc)) xa hanh vai va thiet*.