deletions | additions       diff --git a/Ultimately_though_we_re_interested__.tex b/Ultimately_though_we_re_interested__.tex  index 7d2065b..59bf8de 100644  --- a/Ultimately_though_we_re_interested__.tex  +++ b/Ultimately_though_we_re_interested__.tex 
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where $\left( \frac{d}{dP_{\rm obs}} \right)_{P_{\rm obs} = P_{\rm act}}$ indicates to calculate the $P_{\rm obs}$-derivative of the expression in square brackets and then replace $P_{\rm obs}$ with $P_{\rm act}$.