Perhaps you should try some spelling variations:
nguoi sach » nguoi san, nuoc sach
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
cau thuc » cau truc, cuu thuc, can thuc
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
ve cau » ke cau, va cau, ve cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: nguoi sach ky ((nang ma) or (nang x)) hoi. hieu ve cau thuc van hanh di ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: nguoi sach ky ((nang ma) OR (nang x)) hoi. hieu ve cau thuc van hanh di ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "nguoi sach ky ((nang ma) or (nang x)) hoi. hieu ve cau thuc van hanh di ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: nguoi sach ky ((nang ma) or (nang x)) hoi. hieu ve cau thuc van hanh di ((cua tre) OR (cuu tre))*.