Perhaps you should try some spelling variations:
quan triet » quan tri, quan viet, quan tren
nam thuc » nam thuoc, am thuc, nam thu
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang ma » sang ma, nang cao, mang may
tang ma » mang may, tang van
qua nam » quan nam, cua nam, quang nam
va hanh » va thanh, va danh, ban hanh

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 ky ((nang ma) or (tang ma)) hoi. hieu qua nam thuc ((va hanh) OR (van hanh)) tac quan triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang ma) OR (tang ma)) hoi. hieu qua nam thuc ((va hanh) OR (van hanh)) tac quan triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang ma) or (tang ma)) hoi. hieu qua nam thuc ((va hanh) OR (van hanh)) tac quan triet".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang ma) or (tang ma)) hoi. hieu qua nam thuc ((va hanh) OR (van hanh)) tac quan triet*.