Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, nha thuoc
thuoc dan » thuoc dang, thuc dan, thuoc ban
hieu quan » lieu quan, thien quan, lien quan
cua viet » ca viet, hoa viet, cua vat
hoi nang » hoi lang, ho nang, hoa nang
dan hanh » dang hanh, dan khanh, dan thanh
sach hoi » sach doi, sach moi, cach thoi
hanh di » hanh vi, hanh de, hang di
tu sach » thu sach, su sach, te sach
ma hoi » mai hoi, ma hoa, me hoi
di cua » dai cua, doi cua, de cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach hoi nang ((ma hoi) or (xa hoi)). ((hieu quan) or (hieu qua)) nam thuoc dan hanh di cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach hoi nang ((ma hoi) OR (xa hoi)). ((hieu quan) OR (hieu qua)) nam thuoc dan hanh di cua viet.
• Adding a wildcard symbol may retrieve word variants: tu sach hoi nang ((ma hoi) or (xa hoi)). ((hieu quan) or (hieu qua)) nam thuoc dan hanh di cua viet*.