Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
nang may » mang may, nang ma, bang may
nam thuc » nam thuoc, nam thu, nam tu
danh voi » hanh voi, lanh voi, danh hoa
sach ky » sac ky, sach y, sach ty
may hoi » may thoi, tay hoi, mai hoi
hiem he » hiem xe, hieu he, thien he

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 nang may hoi. hiem he ((nam thuc) OR (am thuc)) va ((danh voi) or (hanh vi)) hoa viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ky nang may hoi. hiem he ((nam thuc) OR (am thuc)) va ((danh voi) OR (hanh vi)) hoa viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ky nang may hoi. hiem he ((nam thuc) OR (am thuc)) va ((danh voi) or (hanh vi)) hoa viet".
• Adding a wildcard symbol may retrieve word variants: hoc sach ky nang may hoi. hiem he ((nam thuc) OR (am thuc)) va ((danh voi) or (hanh vi)) hoa viet*.