Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hanh di » hanh de, hang di, danh di
cua tre » cua te, cuu tre, cua triet
nam tu » nam thu, nam thuc
x hoi » xa hoi, o hoi, x ho

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