  This work addresses more to the technical rather than to the physical
problem, how to calculate analytically the form factor $F(Q)$, the associated
mean-square radius $<r^2>$, and the distribution function $\Phi(x,Q^2)$ for a
given light-cone wave function $\Psi_{q\bar q}(x,\vec k_{\perp})$ of the pion.
They turn out to be functions of only one dimensionless parameter, which is the
ratio of the constituent quark mass and an effective Bohr momentum which
measures the width of the wave function in momentum space. Both parameters are
subject to change in the future, when the presently used solution for the over
simplified $\uparrow\downarrow$-model will be replaced by something better.
Their relation to and agreement with experiment is discussed in detail.
  The procedure can be generalized also to other hadrons.
