anchor.diff:    !-------------------------------------------------------------------------
     ! Subroutine in order to display the critical points
     !-------------------------------------------------------------------------
  -  subroutine display_critical_points(sigma_c_thin, temp_c_thin, sigma_c_thick, temp_c_thick,k)
  -    implicit none
  -
  -    real(kind = x_precision),intent(in) :: sigma_c_thin
  -    real(kind = x_precision),intent(in) :: temp_c_thin
  -    real(kind = x_precision),intent(in) :: sigma_c_thick
  -    real(kind = x_precision),intent(in) :: temp_c_thick
  -    integer                 ,intent(in) :: k
  +  subroutine display_critical_points(sigma_c_thin, temp_c_thin, sigma_c_thick, temp_c_thick, k)
  +    implicit none
  +
  +    real(kind = x_precision), intent(in) :: sigma_c_thin
  +    real(kind = x_precision), intent(in) :: temp_c_thin
  +    real(kind = x_precision), intent(in) :: sigma_c_thick
  +    real(kind = x_precision), intent(in) :: temp_c_thick
  +    integer,                  intent(in) :: k
   
       !------------------------------------------------------------------------
   
       write(*,*)'**** Critical Point',k,'********'
       write(*,*)'****************************************'
  -    write(*,"(' Optically thin (T,sigma) :',1p,E12.4,4x,1p,E12.4)")temp_c_thin, sigma_c_thin
  -    write(*,"(' Optically thick (T,sigma):',1p,E12.4,4x,1p,E12.4)")temp_c_thick, sigma_c_thick
  +    write(*,"(' Optically thin (T, Sigma):',1p,E12.4,4x,1p,E12.4)") temp_c_thin, sigma_c_thin
  +    write(*,"(' Optically thick (T, Sigma):',1p,E12.4,4x,1p,E12.4)") temp_c_thick, sigma_c_thick
       write(*,*)'****************************************'
   
     end subroutine display_critical_points
  
positive.code: 
      call variables(k, T, Smax, f_max, optical_depth, tau_eff)
  
      !write(*,*)'fmin = ',f_min
      !write(*,*)'fmax = ',f_max
  
      if ( f_max * f_min > 0.) then
        !dichotomy = 0
  
  
negative.code:   subroutine variables(k, T, Sigma, f, optical_depth, tau_eff)
      implicit none
  
      real(kind = x_precision), intent(in)  :: T,Sigma
      integer,                  intent(in)  :: optical_depth
      integer,                  intent(in)  :: k
  
      real(kind = x_precision), intent(out) :: f,tau_eff
      !-----------------------------------------------------------------------
      real(kind = x_precision)             :: coeff_a,coeff_b,coeff_c
      real(kind = x_precision)             :: delta
  
  