SYSTEM Tablespace - condensing/compressing

I would like to reduce our 3 data files for the SYSTEM tablespace into one. These have been create due a series of bad decisions and basically occupy to much space, as well as giving the inefficiencies of 3 files. I am reasonably conversant with doing this sort of thing for normal tablespaces, but playing with SYSTEM worries me. Anyone have a simple step by step guide. TIA.

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Anthony Smith