See also

• The MNIST database: http://yann.lecun.com/exdb/mnist/
• A simplified explanation of backpropagation algorithm: http://neuralnetworksanddeeplearning.com/chap2.html
• Another intuitive explanation of backpropagation algorithm: http://cs231n.github.io/optimization-2/
• One more on backpropagation algorithm, it gives detailed information, along with derivation and how it can be applied to different neyworks: https://page.mi.fu-berlin.de/rojas/neural/chapter/K7.pdf