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