Perhaps you should try some spelling variations:
dan thanh » dang thanh, danh thanh, van thanh
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, cam thu
nang xa » nang x, lang xa, nang ma
van cam » van nam, van lam, van cau
sach v » sach va, sach 2, sach vay
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: so ((sach v) OR (sach y)) nang xa hoi. hieu van cam thuc ((dan thanh) or (ban thanh)) dai cua tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach v) OR (sach y)) nang xa hoi. hieu van cam thuc ((dan thanh) OR (ban thanh)) dai cua tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach v) OR (sach y)) nang xa hoi. hieu van cam thuc ((dan thanh) or (ban thanh)) dai cua tu".
• Adding a wildcard symbol may retrieve word variants: so ((sach v) OR (sach y)) nang xa hoi. hieu van cam thuc ((dan thanh) or (ban thanh)) dai cua tu*.