Deep Learning, Ian Goodfellow, Yoshua Bengio, and Aaron Courville, 2016 (MIT Press) - This authoritative textbook provides a comprehensive mathematical and theoretical foundation for recurrent neural networks, covering the basic cell formulation and its components.
Finding structure in time, Jeffrey L. Elman, 1990Cognitive Science, Vol. 14 (John Wiley & Sons)DOI: 10.1207/s15516709cog1402_1 - This foundational paper introduced the Simple Recurrent Network (Elman Network), explicitly describing the architecture and recurrent connections that form the basis of the RNN cell discussed.