Keywords: PK reaction cyclobutadiene.gif en wikipedia 2009 November 4 PK reaction cyclobutadiene en wikipedia Choij CommonsHelper 2005-07-31 V8rik wikipedia en V8rik Original upload log page en wikipedia PK_reaction_cyclobutadiene gif 2005-07-31 16 41 V8rik 354×112× 1505 bytes <nowiki>PK reaction cyclobutadiene </nowiki> Pauson “Khand reaction |