Perhaps you should try some spelling variations:
day hanh » day nhanh, day thanh, dao hanh
cam thuc » am thuc, nam thuc, can thuc
su sach » so sach, vu sach
cam thu » nam thu, cac thu, ca thu
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
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.

• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y ((mang xa) OR (nang ma)) hoi. hieu ve ((cam thuc) OR (cam thu)) day hanh vi cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y ((mang xa) or (nang ma)) hoi. hieu ve ((cam thuc) OR (cam thu)) day hanh vi cua tre~".
• Adding a wildcard symbol may retrieve word variants: su sach y ((mang xa) or (nang ma)) hoi. hieu ve ((cam thuc) OR (cam thu)) day hanh vi cua tre*.