Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
nam thuc » nam thuoc, am thuc, nam tu
sach ky » sac ky, sach y, sach ty
ky mang » ky nang, ke mang, ky dang
may hoi » may thoi, tay hoi, mai hoi
hieu he » hieu ve, hiem he, hieu le
danh vi » hanh vi, danh di, danh va
dinh vi » dinh ve, dinh viet, dinh tri

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

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