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
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
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 ((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 ((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 ((sang ma) or (mang may)) hoi. hieu ve nam thuc vat hanh vi cua viet*.