Dobner, H.-J. “Computing Reliable Error Estimations for Integral Equations With Discontinuities”. Rev. Anal. Numér. Théor. Approx., vol. 27, no. 2, Aug. 1998, pp. 227-36, https://ictp.acad.ro/jnaat/journal/article/view/1998-vol27-no2-art4.