Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
tu sach » thu sach, te sach, tu cach
va hanh » van hanh, va thanh, va danh
cac tac » cac toc, cac bac, cac dac
cau hoa » cau hoi
cao hoa » cao hoat, cao khoa, cao hoc
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet
tac va » tac da, tac xa, tuc va
vi cua » vai cua, di cua

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