Nghiem Van Tinh and Bui Thi Thi 2023. Determining interval lengths for fuzzy time series forecasting model based on index of fuzzy sets by combining hedge algebra and particle swarm optimization. Journal of Military Science and Technology. FEE (Dec. 2023), 271–282. DOI:https://doi.org/10.54939/1859-1043.j.mst.FEE.2023.271-282.