Central bank bond buiys and the re-activation of currency swap lines helped to calm markets' stress, European Central Bank Executive Board member Jose Manuel Gonzalez-Paramo said on Thursday. "Central bank measures have been effective in calming down markets," he said in a speech to a conference. Euro-zone central banks started buying government bonds on Monday as a key part of a $1 trillion bid to resolve the region's debt crisis. Gonzales-Paramo said the ECB would provide details next week on how it plans to sterilise the bond purchases, and other details.