Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
va thanh » gia thanh, va tinh, le thanh
cao hoi » cau hoi, co hoi, cao hoc
van cac » van hac, van cau, van bac
cac dat » cac dan, cai dat, cac dai
sac ky » cac ky, sai ky
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach y) or (sac ky)) nang cao hoi. hieu van cac dat ((va thanh) or (ban thanh)) vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach y) OR (sac ky)) nang cao hoi. hieu van cac dat ((va thanh) OR (ban thanh)) vi cua vat.
• Adding a wildcard symbol may retrieve word variants: thu ((sach y) or (sac ky)) nang cao hoi. hieu van cac dat ((va thanh) or (ban thanh)) vi cua vat*.