Boardgamegeek https://boardgamegeek.com/boardgameexpansion/60054/small-world-leaders-small-world
English - This expansion of Small World is a promotional expansion first given away at Spiel 2009 in Essen. The expansion is based on an idea of Michael Ormesher in a Days of Wonder "Race design contest".
Ludovox http://ludovox.fr/jeu-de-societe/small-world-les-chefs-de-small-world/
French - Une extension pour Small World qui introduit des chefs.
Official https://www.daysofwonder.com/smallworld/fr/special-expansions/
French - Les Chefs de Small World | L'Île du Nécromant