As a  follow-up to my first EPFCG post, I have made a brief but more detailed literature about the matter. It is a little longer so I just have it as a pdf available for download  by following the link below [for educational purposes only, the credibility of the material is based fundamentally on theory]. It includes more insights on what to take note of in the principle of operation and construction of an EPFCG.

[DOWNLOAD]

Also, it is password protected to add a little fun to it.
Perhaps this hint should suffice to give it away:

"The first that you take beside,
your second at first sight."