Perhaps you should try some spelling variations:
dung tren » dung trong, dung trung
doc sach » hoc sach, toc sach, nuoc sach
sach tru » sach truc, sach thu, sach tu
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
va triet » va thiet, va trien, ve triet
tru nang » tra nang, tri nang, truc nano
tuc van » thuc van, truc van, tuc va
hieu va » hieu qua
nang xa » nang x, lang xa, nang ma
cac tuc » cac toc, cac tu, cac tac

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach tru nang xa hoi. ((hieu va) or (lieu va)) cac tuc van hanh tai ((dung tren) or (va triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach tru nang xa hoi. ((hieu va) OR (lieu va)) cac tuc van hanh tai ((dung tren) OR (va triet)).
• Adding a wildcard symbol may retrieve word variants: doc sach tru nang xa hoi. ((hieu va) or (lieu va)) cac tuc van hanh tai ((dung tren) or (va triet))*.