- https://www.cs.cornell.edu/courses/cs1114/2013sp/sections/S06_convolution.pdf
- http://www.aip.de/groups/soe/local/numres/bookcpdf/c13-3.pdf
- http://www.cse.usf.edu/~r1k/MachineVisionBook/MachineVision.files/MachineVision_Chapter4.pdf
- https://web.stanford.edu/class/ee367/slides/lecture6.pdf
- https://pdfs.semanticscholar.org/presentation/50e8/fb095faf6ed51e03c85a2fcb7eb1ae1b1009.pdf
- http://www.robots.ox.ac.uk/~az/lectures/ia/lect2.pdf