Rear speaker wiring on a 106

I've just fitted a Sony CD player to my brother-in-law's 2002 Peugeot 106 'Independence'. I was surprised to find that it appeared to be
wired for front and rear speakers, despite the fact that it only has front speakers currently. I had a look, but it wasn't obvious where the rear speaker wires go to - anyone know?
Thanks in advance :-)
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