Thomson ReutersJanuary 4, 2013 12:20
* Opposition seeking to overturn election results
* President calls for "multi-partisan process"
* Mahama says 2012 GDP growth 8.5 to 9 pct
By Kwasi Kpodo
ACCRA, Jan 4 (Reuters) - Ghana's president called for political unity on Friday, reaching out to rivals who are contesting his election due to suspicions of vote rigging.