  We discuss the interference in the two-particle distribution of the electrons
emitted from two independent superconductors. It is clarified that, while the
interference appearing in the antibunching correlation is due to the Hanbury
Brown and Twiss effect, that in the positive correlation due to
superconductivity is intrinsically different and is nothing but the first-order
interference of Cooper pairs emitted from different sources. This is the
equivalent of the interference of two independent Bose-Einstein condensates.
