An automated heart rate-based algorithm for sleep stage classification: validation using conventional PSG and wearable ECG data - Pini, N.; Chee, M.W.L.; Ong, J.L.; Yilmaz, G.; Chee, N.I.Y.N.; Siting, Z.; Awasthi, A.; Biju, S.; Kishan, K.; Patanaik, A.; Fifer, W.P.; Lucchini, M. (Sleep medicine, 2022)