Deep Learning, Ian Goodfellow, Yoshua Bengio, and Aaron Courville, 2016 (MIT Press) - This textbook explains recurrent neural networks in detail, including the hidden state's function, calculation, and limitations.
Recurrent Neural Networks (CS231n Lecture Notes), Stanford University (CS231n course staff), 2023 - These lecture notes provide a clear, accessible introduction to recurrent neural networks, illustrating the hidden state's operation and its value in sequence processing.
Finding Structure in Time, Jeffrey L. Elman, 1990Cognitive Science, Vol. 14 (Wiley-Blackwell)DOI: 10.1207/s15516709cog1402_1 - This foundational paper describes the Simple Recurrent Network (SRN) and its use of context units (hidden state) to acquire representations of sequential input.