Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach cua » mach cua, cach cua, sac cua
cua viet » ca viet, hoa viet, cua vat
hieu va » lieu va, hieu qua
va chao » va cao, va chat, va cham
doan vi » doan va, don vi, doan thi
ban xa » ban va, ban ma, ban da
dan vi » don vi, dan va, gan vi
xu va » xu van, tu va, su 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 cua ban xa hoi. hieu va chao xu va ((dan vi) or (doan vi)) cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach cua ban xa hoi. hieu va chao xu va ((dan vi) OR (doan vi)) cua viet.
• Adding a wildcard symbol may retrieve word variants: toc sach cua ban xa hoi. hieu va chao xu va ((dan vi) or (doan vi)) cua viet*.