The Effects of Respiratory Sinus Arrhythmia Biofeedback on Heart Rate Variability and Posttraumatic Stress Disorder Symptoms: A Pilot Study. - Zucker, Terri L.; Samuelson, Kristin W.; Muench, Frederick; Greenberg, Melanie A.; Gevirtz, Richard N. (Applied Psychophysiology & Biofeedback, 2009)