Perhaps you should try some spelling variations:
trinh ve » trinh he, trinh vi, trinh viet
trinh va » trinh van, trinh vat, trinh vi
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » lieu va
cac duc » cac du, cao duc, cac dac
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: su sach ky nang xa hoi. ((hieu va) OR (hieu qua)) cac duc va ((trinh ve) or (trinh va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang xa hoi. ((hieu va) OR (hieu qua)) cac duc va ((trinh ve) OR (trinh va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang xa hoi. ((hieu va) OR (hieu qua)) cac duc va ((trinh ve) or (trinh va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang xa hoi. ((hieu va) OR (hieu qua)) cac duc va ((trinh ve) or (trinh va)) cua tre*.