Perhaps you should try some spelling variations:
cam thuc » am thuc, nam thuc, cam thu
hieu van » hieu va, thien van, lieu va
hai hau » hai chau, dai hau, hai hai
hai cau » hai chau, hai chu, hoi cau
va danh » va dinh, va dan, va hanh
thuc va » thuc vat, thuc dan, thuc day
su sach » so sach, vu sach
sach ly » sach y, sach lo, sach ty
nang ma » tang ma, sang ma, mang may
van cam » van nam, van lam, van cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ly ((nang ma) or (nang cao)) hoi. hieu van cam thuc va danh ((hai cau) OR (hai hau)) treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ly ((nang ma) OR (nang cao)) hoi. hieu van cam thuc va danh ((hai cau) OR (hai hau)) treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ly ((nang ma) or (nang cao)) hoi. hieu van cam thuc va danh ((hai cau) OR (hai hau)) treo".
• Adding a wildcard symbol may retrieve word variants: su sach ly ((nang ma) or (nang cao)) hoi. hieu van cam thuc va danh ((hai cau) OR (hai hau)) treo*.