Perhaps you should try some spelling variations:
dua tren » dung tren
sach ty » sach y, sach tu, sach thu
su sach » so sach, vu sach
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
hieu ve » hieu va, hieu van
ve cam » ve cham, ve cac, va cam
tuc va » thuc va, truc va, tuc xa
vi dua » vi du, vi dum, vi lua

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 ty ((nang xa) or (nang ma)) hoi. hieu ve cam ((ban va) or (tuc va)) hanh vi dua tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((nang xa) OR (nang ma)) hoi. hieu ve cam ((ban va) OR (tuc va)) hanh vi dua tren.
• Adding a wildcard symbol may retrieve word variants: su sach ty ((nang xa) or (nang ma)) hoi. hieu ve cam ((ban va) or (tuc va)) hanh vi dua tren*.