Classicthesis, italic in mathmode?

The new version of classicthesis is great! Finally I can enjoy it as a
tetex-user.

Just one question, how do I get the text in mathmode to be in italic,
normally when I use Computer modern as a font this is done by default.
I now I can do it with \textrm{\textit{R}}} but is there a better way?

Simon

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