Finding Structure in Time, Jeffrey L. Elman, 1990Cognitive Science, Vol. 14 (Wiley)DOI: 10.1207/s15516709cog1402_1 - A foundational paper introducing simple recurrent networks (often called 'Elman networks') and their ability to learn temporal dependencies.
Deep Learning, Ian Goodfellow, Yoshua Bengio, and Aaron Courville, 2016 (MIT Press) - Chapter 10 provides a detailed exposition of recurrent neural networks, including the basic RNN architecture and their operation.