seasonal decomposition

[drfg2008]

I'm looking for a good introduction to the subject "seasonal decomposition in SPSS".

(IBM description as I found it  is a little too short:
http://publib.boulder.ibm.com/infocenter/spssstat/v20r0m0/index.jsp?topic=%2Fcom.ibm.spss.statistics.help%2Fidh_seas.htm)