Exploring the Landscape of End User Energy Flexibility: A Systematic Review of Technologies, Challenges, and OpportunitiesMaask, Vahur; Agabus, Hannes; Tiismus, Hans; Astapov, Victor; Ahmadiahangar, Roya; Korõtko, Tarmo; Rosin, ArgoIEEE Access2025 / p. 146579-146602http://doi.org/10.1109/ACCESS.2025.3599989https://ieeexplore.ieee.org/document/11129056