Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
vat hanh » vat thanh, van hanh, va hanh
cua viet » ca viet, hoa viet, cua vat
sach ky » sac ky, sach ty, sach kem
sang ma » tang ma, nang ma, sang tao
hieu ve » hieu va, hieu van
ve nam » he nam, va nam, le nam
vi cua » vai cua, di cua

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 ky) OR (sach y)) ((sang ma) or (mang may)) hoi. hieu ve nam thuc vat hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ky) OR (sach y)) ((sang ma) OR (mang may)) hoi. hieu ve nam thuc vat hanh vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ky) OR (sach y)) ((sang ma) or (mang may)) hoi. hieu ve nam thuc vat hanh vi cua viet".
• Adding a wildcard symbol may retrieve word variants: so ((sach ky) OR (sach y)) ((sang ma) or (mang may)) hoi. hieu ve nam thuc vat hanh vi cua viet*.