Perhaps you should try some spelling variations:
hoc viet » hoc hien
sach kem » hanh kem
nam thuc » nam thuoc, am thuc, nam thu
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
hieu ve » hieu va, hieu van
sach ty » sach y, sach tu, sach thu
ve nam » he nam, va nam, le nam
vi hoc » li hoc, va hoc

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 kem) or (sach ty)) dang ((le hoi) or (ma hoa)). hieu ve nam thuc va hanh vi hoc viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach kem) OR (sach ty)) dang ((le hoi) OR (ma hoa)). hieu ve nam thuc va hanh vi hoc viet.
• Adding a wildcard symbol may retrieve word variants: so ((sach kem) or (sach ty)) dang ((le hoi) or (ma hoa)). hieu ve nam thuc va hanh vi hoc viet*.