Perhaps you should try some spelling variations:
danh dien » dinh dien, danh kien, danh lien
hieu van » hieu va, thien van, lieu va
cau thuc » cau truc, cuu thuc, can thuc
tu sach » thu sach, su sach, te sach
va danh » va dinh, va dan, va hanh
thuc va » thuc vat, thuc dan, thuc day
van cau » van dau, van hau, van chat
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
cuu tre » cua tre, cau tren, cau treo
cu tre » cu tren, cua tre, cu tri

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky ((nang xa) or (nang ma)) hoi. hieu van cau thuc va danh dien ((cu tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (nang ma)) hoi. hieu van cau thuc va danh dien ((cu tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) or (nang ma)) hoi. hieu van cau thuc va danh dien ((cu tre) or (cuu tre))*.