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Liberty, Lee M; Hemphill-Haley, Mark A; Madin, Ian P (2003). "The Portland Hills Fault: uncovering a hidden fault in Portland, Oregon using high-resolution geophysical methods". Tectonophysics. 368 (1–4): 89–103. Bibcode:2003Tectp.368...89L. doi:10.1016/S0040-1951(03)00152-5.