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

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