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 - The seminal paper that widely introduced and popularized the backpropagation algorithm for training multi-layer neural networks.
Deep Learning, Ian Goodfellow and Yoshua Bengio and Aaron Courville, 2016 (MIT Press) - Chapter 6, especially Section 6.5, provides a comprehensive theoretical treatment of backpropagation, forward and backward pass mechanics, and computational graphs.
Neural Networks and Deep Learning, Michael Nielsen, 2015 - Chapter 2 offers a clear, step-by-step derivation and intuitive explanation of the backpropagation algorithm, ideal for beginners.