In a previous article, firstname.lastname@example.org (E. E. Escultura) says:
good one, EEE !!... is this the Ninth Historical perspective upon the Next Theorem of Fermat?
>This enrichment methodlogy capped its achievement with the modern >formulation of Calc. of Var. known as optimal control theory. The >approach is the same: enlarge the space of conventional trajectories >by introducing chattering or probabilistic control and appropriate >metric and taking the closure of the conventional trajectories to >obtain the enlarge space. This not only provides existence theory but >also put the Pontrjagin maximum principle (which is a necessary >condition) on sound foundations free from the Perron paradox. >The comprehensive formulation is Young's book: Lect. on Calc. of Var. >and Opt. Control Theory, W. B. Saunders, 1969. But this book stands on >extensive work of others which we shall list down later.