QFQ stuff

Some errors have been found in the proofs of the published paper by Da Feng <jvfengda at yahoo dot com>

This is a fixed version of the paper, containing the following differences with respect to the published version:

  • pg.5 left column near the bottom
    1) IB U IR ...
    entire item replaced with new text;

  • pg. 8, entire proof of theorem 1 replaced with new proof.
    Last updated: February 18 2015.
    Paolo Valente (paolo DOT valente AT unimore DOT it)