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

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) OR (van nhan)) 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) OR (van nhan)) tai ((dua tren) OR (ve triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach tru nang xa hoi. hieu va cac tuc ((van han) OR (van nhan)) 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) OR (van nhan)) tai ((dua tren) or (ve triet))*.