A method based upon the Laguerre-Gauss quadrature for the integration of Planck’s equation over any specified spectral band is presented. The accuracy of the quadrature, binomial-expansion, and Chebyshev-polynomial methods are determined and compared.
R. Barry Johnson and Elmer E. Branstetter, "Integration of Planck’s equation by the Laguerre-Gauss quadrature method," J. Opt. Soc. Am. 64, 1445-1449 (1974)