How is entropy of a general probability measure defined?



Entropy of a general prob. measure
The Entropy of a function $f$ with respect to a measure $\mu$ is


$$ Ent\_{\mu}(f)=\int f \log f d\mu - \int f d\mu \log(\int f d\mu ) $$


The entropy of a probability distribution $P$ with respect to $\mu$ is given by $ Ent(\frac{dP }{d\mu })$. I a not aware of a general definition that would not implie a reference (here it is $\mu$) measure ... 


