The PON, are well known in the Alchemical world.
Here is the publisher with some resources online :
Here via Mc Lean great site, also texts etc.
You can have videos, books, etc of Jean Dubuis (foundator of PON) on the Triad site.
For beginner, to well advanced practicionners, these courses upon the different aspects of Hermetism are good to read.
Jean Dubuis, the fundator of PON, passed th 9 th of April 2010, at 91 years old.