Charmonium spectrum in an unquenched quark model Sadia Kanwal, Faisal Akram, Bilal Masud and E. S. Swanson Eur. Phys. J. A, 58 11 (2022) 219 Published online: 14 November 2022 DOI: 10.1140/epja/s10050-022-00880-x