Hugo,
My script returns the duplicate listed below, but your's appears to return none.
MemNoYMDStart YMDEndYMDStart YMDEnd
417 2001-10-01 2001-09-30 2001-06-01 2001-09-30
"Do not seek to follow in the footsteps of the wise. Instead, seek what they sought." - Matsuo Basho