As is well known,
e.m. form factors of hadrons contain valuable information on their
quark structure and, particularly, on the hadronic dimensions or charge
distributions. For
example, in a non-relativistic
potential-theory,
assuming an electric charge density 
inside a hadron, with normalization 
, the
electrostatic
potential produced by a spinless, extended hadron turns out to be
where 
is the point-like Coulombic
potential and the form factor 
appears as the
Fourier transform of 
with 
, known as the mean e.m.
squared radius of H, directly connected to its spatial dimensions.
