Perhaps you should try some spelling variations:
hieu luan » hieu luat, hieu quan, hieu quang
tieu luan » tieu chuan, hieu luat, tu luan
phan duc » pham duc, phan tu, phan dau
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
su viet » so viet
nang ma » tang ma, sang ma, nang cao
mang xa » lang xa, mang may, dang xay
sac ky » cac ky, sai ky
tu sac » tu sach, tu cac, tu san

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky ((mang xa) or (nang ma)) hoi. ((hieu luan) OR (tieu luan)) phan duc va hanh va su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((mang xa) OR (nang ma)) hoi. ((hieu luan) OR (tieu luan)) phan duc va hanh va su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky ((mang xa) or (nang ma)) hoi. ((hieu luan) OR (tieu luan)) phan duc va hanh va su viet".
• Adding a wildcard symbol may retrieve word variants: tu sac ky ((mang xa) or (nang ma)) hoi. ((hieu luan) OR (tieu luan)) phan duc va hanh va su viet*.