  In these notes we construct the momentum-space potentials from
configuration-space using for the Fourier-transformation the
Gaussian-Expansion-Method (GEM). This has the advantage that the Fourier-Bessel
integrals can be performed analytically, avoiding possible problems with the
oscillations in the Bessel functions for large r, in particular for $p_f \neq
p_i$. The mass parameters in the exponentials of the Gaussian base-functions
are fixed using the geometric progression recipe of Hiyama-Kamimura. The
fitting of the expansion coefficients is linearly and very fast. Application to
nucleon-nucleon is given in detail for the recent Extended-soft-core model
ESC08c. The NN phase shifts obtained by solving the Lippmann-Schwinger
equations agree very well with those obtained in configuration-space solving
the Schr\"{o}dinger equations.
