https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0217288 Here we can see pictures of those on research gate net: https://www.researchgate.net/publication/333333571_Validation_of_Polar_OH1_optical_heart_rate_sensor_for_moderate_and_high_intensity_physical_activities All of them wonderful scientists. One of them is Prof. Saeid Nahavandi. Director and Pro Vice-Chancellor Defence Technology, Institute for Intelligent Systems Research and Innovation, Deakin University, Australia: https://www.deakin.edu.au/about-deakin/people/saeid-nahavandi & EEE Fellow, Director, IISRI, Deakin University & Harvard University: https://scholar.google.com.au/citations?user=pagzIgsAAAAJ&hl=en Unfortunately, after …