Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
vu sach » vu bach, su sach, vu khach
sach ky » sac ky, sach y, sach ty
nang xa » lang xa, nang ma, mang xa
doi cua » dai cua, hoi cua
cua tu » cua tuc, cua su, cua cu

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ky ((nang xa) or (nang x)) hoi. hieu van nam thuc ((gia thanh) or (ban thanh)) doi cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky ((nang xa) OR (nang x)) hoi. hieu van nam thuc ((gia thanh) OR (ban thanh)) doi cua tu.
• Adding a wildcard symbol may retrieve word variants: vu sach ky ((nang xa) or (nang x)) hoi. hieu van nam thuc ((gia thanh) or (ban thanh)) doi cua tu*.