  It is shown that in deep inelastic electron - ion collisions the detection,
in coincidence with the scattered electron, of a nucleus A-1 in the ground
state, as well as a nucleon and a nucleus A-2 also in the ground state, may
provide unique information on several long standing problems, such as the
origin of the EMC effect, the possible medium modifications of the nucleon
structure functions, and the nature of Nucleon-Nucleon correlations.
