Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, nha thuoc
cua viet » ca viet, hoa viet, cua vat
van hanh » van thanh, ban hanh, van anh
hieu van » thien van, lieu va, hieu ve
va hanh » va thanh, va danh, ban hanh
su sach » so sach, vu sach
sach lo » sach dao, sach doi, sach hoi
nang ma » tang ma, sang ma, nang cao
lo nang » ho nang, ly nang, loai nang
hieu va » lieu va, hieu qua
ma hoi » mai hoi, xa hoi, ma hoa
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 lo nang ma hoi. ((hieu van) or (hieu va)) nam thuoc ((va hanh) OR (van hanh)) vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach lo nang ma hoi. ((hieu van) OR (hieu va)) nam thuoc ((va hanh) OR (van hanh)) vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach lo nang ma hoi. ((hieu van) or (hieu va)) nam thuoc ((va hanh) OR (van hanh)) vi cua viet".
• Adding a wildcard symbol may retrieve word variants: su sach lo nang ma hoi. ((hieu van) or (hieu va)) nam thuoc ((va hanh) OR (van hanh)) vi cua viet*.