http://c4dm.eecs.qmul.ac.uk/audioengine ... ession.pdf
Basically a 'tutorial' composed of a list of recommended articles to be read
edit: There is an answer here : https://www.researchgate.net/publicatio ... d_Analysis
There are two possible topologies for the side-chain, afeedback or feedforward topology. In the feedback topology the input to the side-chain is taken after the gain has been applied. This was traditionally used in early compressors and had the benefit that the side-chain could rectify possible inaccuracies of the gain stage.