Gircys, R., E. Kazanavicius, A. Vrubliauskas, and A. Liutkevicius. “Movement Artefact Resistant Photoplethysmographic Probe”. Elektronika Ir Elektrotechnika, vol. 20, no. 3, Mar. 2014, pp. 73-76, doi:10.5755/j01.eee.20.3.6681.