Dr. Deepa G.S., Dr. Naveen Kumar C.P., and Dr. Smitha Y., “Pulse Oximeter Perfusion Index as an Early Predictor of Successful Ultrasound-Guided Axillary Brachial Plexus Block: A Prospective Observational Study”, IJPRT, vol. 16, no. 1, pp. 1767–1772, Apr. 2026.