Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
dua tren » dung tren
hieu van » hieu va, thien van, lieu va
trung va » truong va, trang va, trung ha
doan vi » doan va, don vi, doan thi
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
truc va » thuc va, thuc vat
nang xa » nang x, lang xa, nang ma
van ha » van hoa, van chat, van hanh

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky nang xa hoi. hieu van ha ((truc va) OR (trung va)) doan vi ((dua tren) or (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky nang xa hoi. hieu van ha ((truc va) OR (trung va)) doan vi ((dua tren) OR (dau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky nang xa hoi. hieu van ha ((truc va) OR (trung va)) doan vi ((dua tren) or (dau tren))".
• Adding a wildcard symbol may retrieve word variants: so sach ky nang xa hoi. hieu van ha ((truc va) OR (trung va)) doan vi ((dua tren) or (dau tren))*.