references to gnu c graph long before i wrote the proposed article gnu c graph i included references under the articles convolution theorem and convolution for the benefit of students and their professors teaching and learning about convolution these references were removed by and notwithstanding my belief that gnu c graph meets the wp notability criteria pointed out external links aren't required to be wp notable just relevant most reasonable people would agree that removing the reference to the only software that easily demonstrates the convolution theorem would be a disservice to the public the text of the references reads under convolution external links gnu c graph a free software package for visualizing the convolution theorem and displaying signals with their spectral plots under convolution theorem additional resources gnu c graph a free software package for demonstrating the convolution theorem and displaying signals with their spectral plots no doubt some wp agf administrator will recognise the educational value and reinstate the references for the benefit of the public