Koesuma, S., M. Ridwan, A. D. Nugraha, S. Widiyantoro, and Y. Fukuda. “Preliminary Estimation of Engineering Bedrock Depths from Microtremor Array Measurements in Solo, Central Java, Indonesia”. Journal of Mathematical and Fundamental Sciences, vol. 49, no. 3, Dec. 2017, pp. 306-20, doi:10.5614/j.math.fund.sci.2017.49.3.8.