Perhaps you should try some spelling variations:
nam thuc » nam thuoc, nam thu, nam tu
day hang » dat hang, dai hang, day nang
hang hoi » hang hoa, hang hai, hang doi
su sach » so sach
vu sach » vu bach, vu khach
hieu ve » hieu va, hieu van
hoi cua » hoi chuc
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
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 ((nam thuc) OR (am thuc)) day hang hoi 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 ((nam thuc) OR (am thuc)) day hang hoi 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 ((nam thuc) OR (am thuc)) day hang hoi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (vu sach)) y nang x hoi. hieu ve ((nam thuc) OR (am thuc)) day hang hoi cua tre*.