Perhaps you should try some spelling variations:
dua tren » dung tren
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
doan vi » doan va, don vi, doan thi
cuu tre » cua tre, cau tren, cau treo
truc va » thuc va, trung va
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: su sach ky nang xa hoi. hieu van ha ((truc va) OR (thuc vat)) doan vi ((dua tren) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang xa hoi. hieu van ha ((truc va) OR (thuc vat)) doan vi ((dua tren) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang xa hoi. hieu van ha ((truc va) OR (thuc vat)) doan vi ((dua tren) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang xa hoi. hieu van ha ((truc va) OR (thuc vat)) doan vi ((dua tren) or (cuu tre))*.