https://www.quora.com/Why-do-neural-networks-need-more-than-one-hidden-layer
https://www.quora.com/How-is-a-convolutional-neural-network-able-to-learn-invariant-features
https://www.quora.com/Why-do-neural-networks-need-more-than-one-hidden-layer
https://www.quora.com/How-is-a-convolutional-neural-network-able-to-learn-invariant-features