Modern chess

Modern chess is a chess variant played on a 9×9 board. The game was invented by Gabriel Vicente Maura in 1968. Besides the usual set of chess pieces, each player has a prime minister and an additional pawn: 
The first match was played in Madrid at Escuela de Bellas Artes de San Fernando's cafe on March 18, 1968. The players were Gabriel Vicente Maura himself (White), and Bonifacio Pedraz Cabezas (Black).
Game rules.
The starting setup is as shown. All the standard rules of chess apply, along with the following special rules:
Optional rule.
In response to criticism that bishops are restricted to only one square color, the inventor proposed an optional new rule, if the players agree:
References.
Bibliography