Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach ty » sach y, sach tu, sach thu
hanh di » hanh de, hang di, danh di
tuc van » thuc van, truc van, tuc va
cam tuc » cam xuc, cam tu, nam thuc
hieu va » lieu va
nang xa » nang x, lang xa, nang ma
ty nang » ky nang, ty xang, ty hang
cua tre » cua te, cuu tre, cua triet

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 ty nang xa hoi. ((hieu va) OR (hieu qua)) cam tuc van ((hanh di) or (hanh vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty nang xa hoi. ((hieu va) OR (hieu qua)) cam tuc van ((hanh di) OR (hanh vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty nang xa hoi. ((hieu va) OR (hieu qua)) cam tuc van ((hanh di) or (hanh vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ty nang xa hoi. ((hieu va) OR (hieu qua)) cam tuc van ((hanh di) or (hanh vi)) cua tre*.