Boardgamegeek https://boardgamegeek.com/boardgameexpansion/181971/power-grid-stock-companies
English - The expansion Power Grid: The Stock Companies offers players a completely new game experience, specifically three new ways to play either Power Grid or Power Grid Deluxe.
Ludovox http://ludovox.fr/jeu-de-societe/haute-tension-les-societes-par-actions/
French - Extension pour Funkenschlag/Power Grid (Haut Tension en français dans le texte).