Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
thuc day » thuc dan, thuc vat
day hanh » day nhanh, day thanh, dao hanh
su sach » so sach, vu sach
hieu ve » hieu va
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
vi cua » vai cua, di cua
x hoi » o hoi, x ho, 5 hoi

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