Reinforcement Learning: An Introduction, Richard S. Sutton and Andrew G. Barto, 2018 (The MIT Press) - Definitive textbook covering the foundations of reinforcement learning, including detailed explanations of TD learning, action-value functions, and the SARSA algorithm.
On-line Q-learning using connectionist networks, Gavin Adrian Rummery, Mahesan Niranjan, 1994Technical Report CUED/F-INFENG/TR166 (Cambridge University Engineering Department) - Original technical report introducing 'Modified Q-learning,' which is the SARSA algorithm, detailing its on-policy TD control approach.
RL Course by David Silver - Lecture 4: Model-Free Control, David Silver, 2015 (Google DeepMind) - Part of a popular lecture series on reinforcement learning, providing clear explanations of model-free control methods, including SARSA and its on-policy characteristics.