Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
bo sach » co sach, hoc sach
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
voi hoa » voi hoat, voi khoa, boi hoa
hieu he » hieu ve, hiem he, hieu le
mai hoi » mai khoi, dai hoi, lai hoi
may hoi » may thoi, tay hoi, may hmi
ky mang » ky nang, ke mang, ky dang
va hoa » van hoa, va hoc, ma hoa
he nam » ha nam, nghe nam

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

• Performing a fuzzy search may retrieve terms with similar spellings: bo sach ky mang ((may hoi) OR (mai hoi)). hieu he nam thuc va hanh ((va hoa) or (voi hoa)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: bo sach ky mang ((may hoi) OR (mai hoi)). hieu he nam thuc va hanh ((va hoa) OR (voi hoa)) viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "bo sach ky mang ((may hoi) OR (mai hoi)). hieu he nam thuc va hanh ((va hoa) or (voi hoa)) viet".
• Adding a wildcard symbol may retrieve word variants: bo sach ky mang ((may hoi) OR (mai hoi)). hieu he nam thuc va hanh ((va hoa) or (voi hoa)) viet*.