Perhaps you should try some spelling variations:
dang thanh » dong thanh, dang hanh, hoang thanh
thuc dang » thuoc dang, thuc dan, thuc dung
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, cam thu
van cam » van nam, van lam, van cau
doi cua » hoi cua
so sach » bo sach, co sach, hoc sach
nang xa » nang x, lang xa, nang ma
ly nang » ky nang, ly hang, ly vang
so sanh » do sanh

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) or (so sanh)) ly nang xa hoi. hieu van cam thuc dang thanh ((doi cua) OR (dai cua)) tu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((so sach) OR (so sanh)) ly nang xa hoi. hieu van cam thuc dang thanh ((doi cua) OR (dai cua)) tu.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((so sach) or (so sanh)) ly nang xa hoi. hieu van cam thuc dang thanh ((doi cua) OR (dai cua)) tu".
• Adding a wildcard symbol may retrieve word variants: ((so sach) or (so sanh)) ly nang xa hoi. hieu van cam thuc dang thanh ((doi cua) OR (dai cua)) tu*.