Librodo, J.R. and Daza, M.R.H. 1997. Detection of surface defects on carbon black samples by the piezoelectric photoacoustic technique. Proceedings of the Samahang Pisika ng Pilipinas, 15(1), SPP-1997-IC-05. URL: https://proceedings.spp-online.org/article/view/SPP-1997-IC-05.