Perhaps you should try some spelling variations:
hieu viec » nhieu viec, hieu ve, sieu viet
van thanh » ban thanh, van tuan
viec anh » viet anh, viec tang, viec binh
anh quoc » dang quoc, han quoc, anh duc
quoc van » quoc va, quoc ban, quoc lan
thanh co » thanh do, thanh ca, thanh ho
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
cua tre » cua te, cuu tre, cua triet
co cua » con cua, ca cua, cong cua
o hoc » mo hoc, so hoc, y hoc

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 ty nang ((o hoc) or (co hoc)). hieu viec anh quoc van thanh co cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((o hoc) OR (co hoc)). hieu viec anh quoc van thanh co cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((o hoc) or (co hoc)). hieu viec anh quoc van thanh co cua tre*.