Causal Inference for The Brave and True, Matheus Facure Alves, 2022 - An accessible online textbook that offers practical examples and theoretical background for causal inference, including detailed explanations of meta-learners.
CausalML Documentation: Meta-Learners, CausalML Developers, 2024 - Provides practical examples and API specifications for implementing S-Learner, T-Learner, and X-Learner using Python's CausalML library.