Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
tu sach » thu sach, su sach, te sach
sach vu » sach va, sach tu, sach uu
nang ma » tang ma, sang ma, mang may
va cham » va chat, va tham
vuc van » luc van, thuc van, chuc van
duc van » duc va, duc tan, duc manh
hanh ki » hanh vi, hanh ky, hanh kien
ki su » ky su

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 vu ((nang ma) or (nang cao)) hoi. lieu va cham ((vuc van) OR (duc van)) hanh ki su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach vu ((nang ma) OR (nang cao)) hoi. lieu va cham ((vuc van) OR (duc van)) hanh ki su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach vu ((nang ma) or (nang cao)) hoi. lieu va cham ((vuc van) OR (duc van)) hanh ki su triet".
• Adding a wildcard symbol may retrieve word variants: tu sach vu ((nang ma) or (nang cao)) hoi. lieu va cham ((vuc van) OR (duc van)) hanh ki su triet*.