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