Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
xa dinh » xac dinh, va dinh, ba dinh
dinh ca » dinh cac, dinh cua, dinh cao
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
me hoi » le hoi
cac te » cac he, cac tu, cac ke
ca cua » co cua
te xa » te va

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach y nang ((me hoi) or (ma hoa)). hieu va cac te xa dinh ca cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((me hoi) OR (ma hoa)). hieu va cac te xa dinh ca cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((me hoi) or (ma hoa)). hieu va cac te xa dinh ca cua tre*.