Perhaps you should try some spelling variations:
hieu viec » nhieu viec, hieu ve, sieu viet
viec dat » vien dai, vien da, viec lam
thuc van » thuc dan, thuc va, thuc hanh
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
nang xa » nang x, lang xa, nang ma
hanh di » hanh de, hang di, danh di
cua tre » cua te, cuu tre, cua triet

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