Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
van hanh » van thanh, ban hanh, van anh
sang mai » sang ma, sang tai, lang mai
mai khoi » mai khoa, tai khoa, cac khoi
va hanh » va thanh, va danh, ban hanh
cam tuc » cam xuc, cam tu, nam thuc
sach ky » sac ky, sach y, sach ty
sach tu » sach thu, cach tu, sach ty
hieu va » lieu va, hieu qua
va cam » va cham, va cac, va cao

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) or (sach tu)) sang mai khoi. hieu va cam tuc ((va hanh) OR (van hanh)) mai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sach tu)) sang mai khoi. hieu va cam tuc ((va hanh) OR (van hanh)) mai va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) or (sach tu)) sang mai khoi. hieu va cam tuc ((va hanh) OR (van hanh)) mai va triet".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sach tu)) sang mai khoi. hieu va cam tuc ((va hanh) OR (van hanh)) mai va triet*.