Complete set of five announcement cards / an artist's project for Robert Barry's "Invitation Series. Includes: a double sided card / announcement "Leo Castelli Invites You to An Exhibition by Robert Barry at Yvon Lambert/Paris During the Month of February 1973;" a single sided card / announcement "Yvon Lambert Invites You to an Exhibition by Robert Barry at Galerie MTL Brussels During the Month of March 1973;" a double sided card / announcement "Galerie MTL Invites You to an Exhibition by Robert Barry at Galleria Toselli, Milan During the Month of April 1973;" a double sided card / announcement "Galerie Toselli Invites You to an Exhibition by Robert Barry at Galleria Sperone, Turin During the Month of May 1973;" a double sided card / announcement "Paul Maenz, Cologne, Invites You to an Exhibition by Robert Barry at Art & Project, Amersterdam During the Month of November 1972;" a single sided card / announcement "Gian Enzo Sperone Invites You to An Exhibition by Robert Barry at Paul Maenz, Cologne, During the Month of June 1973;" Single sided page / exhibition announcement "Art & Project Invites You to An Exhibition by Robert Barry at Jack Wendler Gallery, London, During the Month of December 1972;" and a single sided card / announcement "Jack Wendler Invites You to an Exhibition by Robert Barry at Leo Castelli Gallery, New York During the Month of January, 1973."