Perhaps you should try some spelling variations:
hieu viec » nhieu viec, hieu ve, sieu viet
viec day » viec dat, viec xay, viec hay
su sach » so sach, vu sach
ty nang » ty xang, ty hang, ly nang
thuc va » thuc dan, thuc day
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
di cua » dai cua, doi cua, de cua

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