Perhaps you should try some spelling variations:
dat tren » dat trong, dua tren
dau tren » dau tien, dau tieng, dau trong
ban hanh » ban hang
cham tu » pham tu, cam tu, chai tu
hieu vu » hieu va, hieu ve, hieu su
tu sach » thu sach, su sach, te sach
lang ha » long ha
nang xa » nang x, lang xa, nang ma
vu cham » va cham, vu kham, tu cham
tu ban » thu ban, te ban

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach y ((nang xa) or (lang ha)) hoi. hieu vu cham tu ban hanh vi ((dau tren) OR (dat tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang xa) OR (lang ha)) hoi. hieu vu cham tu ban hanh vi ((dau tren) OR (dat tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((nang xa) or (lang ha)) hoi. hieu vu cham tu ban hanh vi ((dau tren) OR (dat tren))".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang xa) or (lang ha)) hoi. hieu vu cham tu ban hanh vi ((dau tren) OR (dat tren))*.