  p-3H and n-3He scattering in the energy range above the n-3He but below the
d-d thresholds is studied by solving the 4-nucleon problem with a realistic
nucleon-nucleon interaction. Three different methods -- Alt, Grassberger and
Sandhas, Hyperspherical Harmonics, and Faddeev-Yakubovsky -- have been employed
and their results for both elastic and charge-exchange processes are compared.
We observe a good agreement between the three different methods, thus the
obtained results may serve as a benchmark. A comparison with the available
experimental data is also reported and discussed.
