Perhaps you should try some spelling variations:
hieu luan » hieu luat, hieu quan, tieu luan
phan duc » phan tu, phan dau, tran duc
su triet » su viet, su tien, ve triet
nang ma » tang ma, sang ma, nang cao
mang xa » lang xa, mang may, dang xay
va danh » va dinh, va dan, va hanh
danh vi » hanh vi, dinh vi, danh di
tu sach » thu sach, su sach, te sach
vi su » va su, ve su, ki 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 y ((mang xa) or (nang ma)) hoi. hieu luan ((phan duc) OR (pham duc)) va danh vi su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((mang xa) OR (nang ma)) hoi. hieu luan ((phan duc) OR (pham duc)) va danh vi su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((mang xa) or (nang ma)) hoi. hieu luan ((phan duc) OR (pham duc)) va danh vi su triet".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((mang xa) or (nang ma)) hoi. hieu luan ((phan duc) OR (pham duc)) va danh vi su triet*.