Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach tru » sach truc, sach thu, sach tu
tru nang » tra nang, tri nang, truc nano
dua tren » dung tren
ve triet » va trien, su triet
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
cac tuc » cac toc, cac tu, cac tac
tuc van » thuc van, truc van, tuc va
van han » van hanh, van phan, van nhan
han tai » hang tai, nhan tai, van tai

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 tru nang xa hoi. hieu va cac tuc van han tai ((dua tren) or (ve triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach tru nang xa hoi. hieu va cac tuc van han tai ((dua tren) OR (ve triet)).
• Adding a wildcard symbol may retrieve word variants: toc sach tru nang xa hoi. hieu va cac tuc van han tai ((dua tren) or (ve triet))*.