Learning representations by back-propagating errors, David E. Rumelhart, Geoffrey E. Hinton, and Ronald J. Williams, 1986Nature, Vol. 323 (Springer Nature)DOI: 10.1038/323533a0 - Original paper introducing the backpropagation algorithm, making it widely known and applied to multi-layer neural networks.
Deep Learning, Ian Goodfellow, Yoshua Bengio, and Aaron Courville, 2016 (MIT Press) - Comprehensive textbook covering backpropagation with mathematical rigor and its role in deep learning.
Neural Networks and Deep Learning, Michael Nielsen, 2019 (Determination Press) - An accessible online book offering a step-by-step explanation of the backpropagation algorithm.
Backpropagation, Intuitions, Stanford CS231n Course Staff, 2019 (Stanford University) - Course notes providing a practical and intuitive explanation of backpropagation, including its derivations.