scikit-learn: Gradient Boosting, scikit-learn developers, 2024 (scikit-learn project) - Official documentation describing the implementation of gradient boosting and the learning_rate parameter.
XGBoost: A Scalable Tree Boosting System, Tianqi Chen, Carlos Guestrin, 2016Proceedings of the 22nd ACM SIGKDD International Conference on Knowledge Discovery and Data Mining (ACM)DOI: 10.1145/2939672.2939785 - This paper discusses regularization techniques, including shrinkage (learning rate), within the context of the XGBoost algorithm.