Test of the Flavour Independence of alpha_s using                              
Next-to-leading Order Calculations for Heavy Quarks                            
  
     We present a test of the flavour independence of the strong               
     coupling constant for charm and bottom quarks with respect                
     to light (uds) quarks.  Five observables related to global event          
     shapes were used to measure alpha_s in three flavour tagged               
     samples (uds, c and b).  The event shape distributions were               
     fitted by second order calculations of jet production taking into         
     account mass effects for the c and b quarks.   We find the ratio          
     of alpha_s from c events to uds events to be                              
     0.997+-0.038(stat.)+-0.030(syst.)+-0.012(theory).  The corresponding      
     quantity between b and uds events is                                      
     0.993+-0.008(stat.)+-0.006(syst.)+-0.011(theory).                         
  
 Parallel session :3                   
 Plenary  session :11