Perhaps you should try some spelling variations:
hieu cac » hieu luc, hieu va, hieu van
hien cac » thien cac, vien cac, dien cac
dinh ve » dinh ket, dinh van
dinh va » dinh van, tinh va, sinh va
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cuu tre, cua triet
lao va » tao va, cao va, bao va

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang xa hoi. hieu ((hien cac) OR (hieu cac)) lao va ((dinh va) or (dinh ve)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang xa hoi. hieu ((hien cac) OR (hieu cac)) lao va ((dinh va) OR (dinh ve)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang xa hoi. hieu ((hien cac) OR (hieu cac)) lao va ((dinh va) or (dinh ve)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. hieu ((hien cac) OR (hieu cac)) lao va ((dinh va) or (dinh ve)) cua tre*.