1. Akbar, S. A., & Yudhana, A. (2014). Vibration Belt as a Directional Aid for the Visually Impaired. Synergy, 18(2), 71-76.
2. Andreas, & Wendanto, W. (2017). Obstacle Detection Blind Assistive Stick Using Arduino Microcontroller Based Ultrasonic Sensor. Go Infotech: Scientific Journal of STMIKAUB, 22(1).
3. Aqli, K. C., Nurussa'adah, N., & Abidin, Z. (2014). Design of an Indoor Voiced Mobility Aid for the Visually Impaired Based on RFID (Radio Frequency Identification). TEUB Student Journal, 1(5).
4. Heryanto, M. A., & Suprijono, H. (2011). Application of Ultrasound Wave on White Stick for Early Warning for Blind People. DIAN JOURNAL, 11(1).
5. Hill, E. W. and Blasch, B. B. (1980). Concept development. In. R. L., Welsh and B. B., Blasch(eds.), Foundations of orientation and mobility (pp. 265- 290). New York: American Foundation for the Blind.