Germany Looking at Citigroup Bond Trading  BERLIN (Reuters) - Germany's financial watchdog said on  Thursday it was looking into recent trading by U.S. financial  services group Citigroup &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=C.N target=/stocks/quickinfo/fullquote"&gt;C.N&lt;/A&gt; in European government bond and  derivative markets, but had not started a formal probe.