  The present manuscript concerns the calculation of the boson-boson scattering
length for the composite bosons that form as bound-fermion pairs in the
strong-coupling limit of the BCS-BEC crossover. The material presented in this
manuscript was already published as a part of a longer paper on the BCS-BEC
crossover problem (P. Pieri and G.C. Strinati, Phys. Rev. B 61, 15370 (2000)).
Given the recent experimental advances on the formation of ultracold bosonic
molecules from a Fermi gas of atoms by a Feshbach resonance, the calculation of
the boson-boson scattering length has now become of particular interest. The
present short version of the above paper could thus be helpful to the
scientific community working on ultracold atomic gases. Accordingly, the
present manuscript is intended for circulation as a preprint only.
