STABILITY OF THE SPECTRUM FOR TRANSFER OPERATORS
                                        
                               by
                               
                Gerhard Keller  and Carlangelo Liverani
                            
                              
ABSTRACT: 
We prove stability of the isolated eigenvalues  of transfer operators 
satisfying a Lasota-Yorke type inequality under a broad class of random 
and non--random perturbations including Ulam-type discretizations. 
The results are formulated in an abstract framework.