On the fine spectrum of the forward difference operator on the Hahn   space
  The main purpose of this paper is to determine the fine spectrum with respect to Goldberg's classification of the difference operator over the sequence space h. As a new development, we give the approximate point spectrum, defect spectrum and compression spectrum of the difference operator on the sequence space h. 
Medine Ye\c{s}ilkayagil, Murat Kiri\c{s}ci
math.FA