text: #ifndef SECULAR_EQUATION_H_INCLUDED
  #define SECULAR_EQUATION_H_INCLUDED
  
  #include "matrix.h"
  
  long double solve_secular_equation(long double rho, const matrix_type_t D, const matrix_type_t v_prime, unsigned i, long double lambda_init, unsigned n_deflated, long double eps);
  
  #endif  /* SECULAR_EQUATION_H_INCLUDED */
  