Perhaps you should try some spelling variations:
hieu vien » hieu viec, thieu nien, hieu tieng
hieu hien » bieu hien, dieu hien, chieu chien
tu sach » thu sach, te sach, tu cach
va hanh » van hanh, va thanh, va danh
cac dac » cac dan, cac dai, cac bac
cua tre » cua te, cuu tre, cua triet
su sach » so sach, vu sach
y nang » ky nang, ly nang, v nang
dac va » duc va, day va, dat va
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) OR (su sach)) y nang x hoi. ((hieu vien) or (hieu hien)) cac dac va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) y nang x hoi. ((hieu vien) OR (hieu hien)) cac dac va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (su sach)) y nang x hoi. ((hieu vien) or (hieu hien)) cac dac va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (su sach)) y nang x hoi. ((hieu vien) or (hieu hien)) cac dac va hanh vi cua tre*.