Perdana FW, Ayuni SD, Wisaksono A, Syahrorini S. Prototype Social Distancing Reminder Using HC-SR04 Sensor At The Payment Counter Via A Smartphone. PELS [Internet]. 2021Jul.14 [cited 2024Apr.23];1(2). Available from: https://pels.umsida.ac.id/index.php/PELS/article/view/952