Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, nha thuoc
sach thu » sach thue, sach thieu, sach tham
cua viet » ca viet, hoa viet, cua vat
sach ty » sach y, sach tu, xach tay
may hoi » may thoi, tay hoi, mai hoi
hieu ve » hieu va, hieu van
va hanh » van hanh, va thanh, va danh
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: su ((sach ty) OR (sach thu)) mang may hoi. hieu ve ((am thuc) or (nam thuoc)) va hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach thu)) mang may hoi. hieu ve ((am thuc) OR (nam thuoc)) va hanh vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) OR (sach thu)) mang may hoi. hieu ve ((am thuc) or (nam thuoc)) va hanh vi cua viet".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) OR (sach thu)) mang may hoi. hieu ve ((am thuc) or (nam thuoc)) va hanh vi cua viet*.