In addition to the locals and provisionals, a great variety of overprints and surcharges were added to stocks of existing stamps by the powers then in control. Although many of these were printed on the stamps, they are commonly known by Mexican philatelists as "gomigrafos" or rubber stamps. Among the best known of these overprints are the "GCM" monograms, standing for "Gobierno Constitucionalista Mexicano" or the "Constitutional Mexican Government." Varieties of this overprint were first used by the Conventionalists supported by Villa, and later by the Constitutionalists and known as the Carranza overprints.