Perhaps you should try some spelling variations:
dua tren » dung tren
hieu van » hieu va, thien van, lieu va
cu tren » tu tren
tinh va » tich va, trinh van, trinh vat
va tinh » may tinh
sach ky » sach y, sach ty, sach kem
van cau » van dau, van hau, van chat
nang xa » nang x, lang xa, nang ma
cau tu » dau tu, cau truc
sac ky » cac ky, sai ky

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

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