|   | 
            | 
          Abstract: | 
           
              We use the results of Zhang [15,16] and Davies [7] on the behavior of the heat kernel   on a bounded   domain   to find again the result of Grunau-Sweers [9] concerning the estimates of the iterated Greens functions   . Next, we use these estimates to characterize, by means of  , the Kato class    and we give new examples of functions belonging to this class. 
             
          
         |