Two-point theory for the differential self-interrogation Feynman-alpha method J. Anderson, D. Chernikova, I. Pázsit, L. Pál and S. A. Pozzi Eur. Phys. J. Plus, 127 8 (2012) 90 Published online: 28 August 2012 DOI: 10.1140/epjp/i2012-12090-2