Alfina Nadhirotussolikah, A. Pudji, and Muhammad Ridha Mak’ruf. “Fetal Doppler Simulator Based on Arduino”. Journal of Electronics, Electromedical Engineering, and Medical Informatics, Vol. 2, no. 1, Jan. 2020, pp. 28-32, doi:10.35882/jeeemi.v2i1.6.