Perhaps you should try some spelling variations:
cam thuc » nam thuc, cam thu, can thuc
day hanh » day nhanh, day thanh, dao hanh
su sach » so sach
vu sach » vu bach, vu khach
hieu ve » hieu va, hieu van
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
di cua » dai cua, doi cua, de 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: ((su sach) or (vu sach)) y nang x hoi. hieu ve ((cam thuc) OR (am thuc)) day hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (vu sach)) y nang x hoi. hieu ve ((cam thuc) OR (am thuc)) day hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (vu sach)) y nang x hoi. hieu ve ((cam thuc) OR (am thuc)) day hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (vu sach)) y nang x hoi. hieu ve ((cam thuc) OR (am thuc)) day hanh di cua tre*.