Calayag, A.B. and Altoveros, N.C. 2004. Low cost PC-based instrument for monitoring long period one-dimensional horizontal ground motion using Lehman seismometer. Proceedings of the Samahang Pisika ng Pilipinas, 22(1), SPP-2004-PA-09. URL: https://proceedings.spp-online.org/article/view/SPP-2004-PA-09.