Daoud, Salah, et al. “Elastic Constants and Optical Phonon Frequencies of BX (X= P, As, and Sb) Semiconductors: Semi-Empirical Prediction”. International Journal of Physical Research, vol. 8, no. 2, Sept. 2020, pp. 45-49, https://doi.org/10.14419/ijpr.v8i2.31001.