nd in many textbooks,
        see for example: E. Ott "Chaos is Dynamical Systems", Cambridge.
      </p>
<p>
        To calculate the Lyapunov exponents numerically one usually solves the equations
        of motion for <span class="emphasis"><em>n</em></span> perturbations and orthonormalizes them
        every <span class="emphasis"><em>k</em></span> steps. The Lyapunov exponent is the average
        of the logarithm of the stretching factor of each perturbation.
      </p>
<p>
        To demonstrate ho