. . . . . . . "10.3390/s20071923" . . . . . . . "20" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "20" . . . . . . . "dc1fd12e3bac8b6f3d05ac66a8ac6614970dc4cf" . "10.3390/s20071923" . . "Enhancing the Robustness of Smartphone Photoplethysmography: A Signal Quality Index Approach" . . . . . . . . . "1923" . . . . . . . . . "MDPI AG" . . . . . "2020-03-30"^^ . . . . . "1923" . . . . "10.3390/s20071923" . . . . .