Perhaps you should try some spelling variations:
su sach » so sach, vu sach
va hanh » van hanh, va thanh, va danh
cao duc » dao duc, cao suc, giao duc
cao luc » bao luc, cao suc, cau luc
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
mang xa » lang xa, mang may, dang xay
cua tre » cua te, cuu tre, cua triet
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: su sach ty ((mang xa) or (nang x)) hoi. hieu va ((cao luc) OR (cao duc)) va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((mang xa) OR (nang x)) hoi. hieu va ((cao luc) OR (cao duc)) va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty ((mang xa) or (nang x)) hoi. hieu va ((cao luc) OR (cao duc)) va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ty ((mang xa) or (nang x)) hoi. hieu va ((cao luc) OR (cao duc)) va hanh vi cua tre*.