Maulana, P., U. Darusalam, and N. D. Nathasia. “Road Guides and Special Location Monitoring for Blind People Using Ultrasonic Sensors and Microcontroller-Based GPS Modules: Road Guides and Special Location Monitoring for Blind People Using Ultrasonic Sensors and Microcontroller-Based GPS Modules”. Jurnal Mantik, vol. 3, no. 4, Feb. 2020, pp. 444-50, https://www.ejournal.iocscience.org/index.php/mantik/article/view/590.