Nobo, Jorge Luis.  "Whitehead's Principle of Relativity."  Process Studies 8, no. 1 (Spring 1978): 1-20.

Abstract

I argue, through a series of textual considerations, that Whitehead's principle of relativity must be understood as asserting that to be an entity is both to have a potentiality for being repeated and to have that potentiality realized in every actual occasion whose becoming finds that entity already existing as a fully determinate being.  Thus understood, I argue, the principle implies that every completed occasion in the universe of a novel occasion is reproduced in and for that occasion.  I further argue for the correctness of my interpretation by examining its bearing on the mutual immanence of occasions, the ontological principle, and the category of the ultimate.  [Abstract from The Philosopher's Index]