  A zero range approach is used to model resonant two-body interactions between
three identical bosons. A dimensionless phase parametrizes the three-body
boundary condition while the scattering length enters the Bethe-Peierls
boundary condition. The model is solved exactly at zero energy for any value of
the scattering length, positive or negative. From this solution, an analytical
expression for the rate of three-body recombination to the universal shallow
dimer is extracted.
