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                  >PDF</a
                >
              </li>
              <li>
                Spergel, D. N. and Steinhardt, P. J., “Observational Evidence
                for Self-Interacting Cold Dark Matter”,
                <i>Physical Review Letters</i>, vol. 84, no. 17, pp. 3760–3763,
                2000. doi:10.1103/PhysRevLett.84.3760.
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