# Symbol for relative entropy

Could you help me with typesetting the following symbol (marked by red frame):

I searched over all possible manuals but was not able to find it. It looks like capital D, but actually it is not the same.

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Do you have a pdf source of this picture? Then we can at least identify the font. –  mafp Mar 15 '13 at 23:19
No, unfortunately I do not have a pdf. It is from the book "probabilistic graphical models" by Daphne Koller and Nir Friedman, page 42 –  iensen Mar 15 '13 at 23:23
Could $\mathbb{D}$ be a valid approximation? –  JLDiaz Mar 15 '13 at 23:24
For me \mathbb{D} gives a different symbol with a double frame. –  iensen Mar 15 '13 at 23:29

It looks to me like a constructed symbol (and even if it is a font, it may be easier to construct the symbol than find the font). For example:

\documentclass{article}

\begin{document}

$I\mkern-8muD((p,1-p)$

\end{document}

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Great! Thank you. I didn't know we can construct symbols. –  iensen Mar 15 '13 at 23:33