Jiahui Z, Supattarachaiwong W. [RETRACTED ARTICLE] A Compilation of Bel Canto Vocal Exercises for Middle School Students. JBER [internet]. 2025 Dec. 24 [cited 2026 Aug. 28];11(4):641-50. available from: https://so06.tci-thaijo.org/index.php/jber/article/view/286724