kronrod_rule_test, a Fortran90 code which calls kronrod_rule(), which computes both a Gauss-Legendre quadrature rule of order N, and the Gauss-Kronrod rule of order 2*N+1.
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kronrod_rule, a Fortran90 code which computes a Gauss and Gauss-Kronrod pair of quadrature rules of arbitrary order, by Robert Piessens, Maria Branders.