Some links for study:
https://yashk2810.github.io/Applying-Convolutional-Neural-Network-on-the-MNIST-dataset/
http://parneetk.github.io/blog/cnn-mnist/
https://towardsdatascience.com/a-simple-2d-cnn-for-mnist-digit-recognition-a998dbc1e79a
http://cs231n.github.io/convolutional-networks/
https://www.katacoda.com/basiafusinska/courses/tensorflow-getting-started/tensorflow-mnist-beginner
http://neuralnetworksanddeeplearning.com/chap1.html
https://codelabs.developers.google.com/codelabs/cloud-tensorflow-mnist/#0
https://www.oreilly.com/learning/not-another-mnist-tutorial-with-tensorflow
https://data-flair.training/blogs/tensorflow-mnist-dataset/
https://www.geeksforgeeks.org/applying-convolutional-neural-network-on-mnist-dataset/