The Use of Heart Rate Variability-Biofeedback (HRV-BF) as an Adjunctive Intervention in Chronic Fatigue Syndrome (CSF/ME) in Long COVID: Results of a Phase II Controlled Feasibility Trial. - Cossu, Giulia; Kalcev, Goce; Primavera, Diego; Lorrai, Stefano; Perra, Alessandra; Galetti, Alessia; Demontis, Roberto; Tramontano, Enzo; Bert, Fabrizio; Montisci, Roberta; Maleci, Alberto; Castilla, Pedro José Fragoso; et al. (Journal of Clinical Medicine, 2025)