docs: def mimf_ferrario(mi):
      ''' Curvature MiMf from Ferrario etal. 2005MNRAS.361.1131.'''
      
      mf=-0.00012336*mi**6+0.003160*mi**5-0.02960*mi**4+\
        0.12350*mi**3-0.21550*mi**2+0.19022*mi+0.46575
      return mf