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Biot MA, Willis DG (1957). "The elastic coefficients of the theory of consolidation". Journal of Applied Mechanics. 24 (4): 594–601. Bibcode:1957JAM....24..594B. doi:10.1115/1.4011606.
Plona T (1980). "Observation of a Second Bulk Compressional Wave in a Porous Medium at Ultrasonic Frequencies". Applied Physics Letters. 36 (4): 259. Bibcode:1980ApPhL..36..259P. doi:10.1063/1.91445.
Gassmann F (1951). "Über die Elastizität poröser Medien". Vierteljahrsschrift der Naturforschenden Gesellschaft in Zürich. 96: 1–23. (English translation available as pdf here)