Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
tu sach » thu sach, su sach, te sach
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
nam tu » nam thu, nam thuc
vi cua » vai cua, di cua
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 y nang x hoi. ((hieu quan) or (hieu qua)) nam tu va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang x hoi. ((hieu quan) OR (hieu qua)) nam tu va hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach y nang x hoi. ((hieu quan) or (hieu qua)) nam tu va hanh vi cua tre*.