I've come across the Onsager reciprocal principle. It's almost clear, except for thermodynamic conjugate quantities - what's that, physical meaning (except the formal definitions: $X_i = -\frac{1}{k}\frac{\partial S}{\partial x_i}$, which isn't clear) and why:

\begin{equation}
  \langle X_i\cdot x_k\rangle = \delta_{ik}
\end{equation}

The Wikipedia is lack for references in this article.


Question: Can you demonstrate in Python how to post an ad to Facebook's ads API?
Answer: This https://github.com/facebook/fbconsole/blob/master/src/fbconsole.py was a great starting point for me when I did what I needed to do with Facebook, although I did not do ads with it.