Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
nang ma » tang ma, sang ma, nang cao
sach ty » sach y, sach tu, sach thu
van cac » van hac, van cau, van bac
cac bac » cac bai, cac ban, cac cach
bac ban » cac ban, bac can, bac dan
nang xa » nang x, lang xa, mang xa
lap cua » lai cua, tap cua, ap cua
lam cua » nam cua, lam chat
tu sach » thu sach, su sach, te sach

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 ty ((nang xa) or (nang ma)) hoi. hieu van cac bac ban thanh ((lap cua) or (lam cua)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((nang xa) OR (nang ma)) hoi. hieu van cac bac ban thanh ((lap cua) OR (lam cua)) viet.
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((nang xa) or (nang ma)) hoi. hieu van cac bac ban thanh ((lap cua) or (lam cua)) viet*.