etize the problem by specifying a sequence of n (perhaps equally
      spaced) points x, and applying standard finite difference approximations
      to the derivatives in the continuous equation.  A piecewise linear discretization 
      of the solution can then be computed by bsv().
    </p>

    <p>
      When alpha and beta have opposite sign, the solution must cross the
      x-axis (at least once).  The location x0 of this crossing is of interest,
      and can be computed by bsv_crossing().
    </p>
