Correlations in photon-numbers and integrated intensities in parametric processes involving three optical fieldsJ. Peřina, J. Křepelka, J. Peřina, M. Bondani, A. Allevi and A. AndreoniEur. Phys. J. D, 53 3 (2009) 373-382DOI: https://doi.org/10.1140/epjd/e2009-00136-3