A criterion for subharmonicity of a function of the spectrum
Volume 75 / 1982
                    
                    
                        Studia Mathematica 75 (1982), 37-49                    
                                        
                        DOI: 10.4064/sm-75-1-37-49                    
                                    
                                                                
                             
             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                             
                                                         
                                                            