National Gallery of Modern Art's collection of Dada and Surrealism is regarded as one of the best and most complete in the world: it features masterpieces by artists such as Max Ernst, René Magritte, Joan Miró, Paul Delvaux, Yves Tanguy, Alberto Giacometti and Marcel Duchamp. The collection is also rich in archival material, ranging from letters and manuscripts to artists' books featuring unique drawings and inscriptions. The collection is rich thanks to two major sources: Roland Penrose (1900-1984) and Gabrielle Keiller (1908-1995). A celebrated British artist, author and close confidant of Picasso, Penrose was also a collector, assembling one of the greatest collections of early twentieth-century cubist and surrealist art. Gabrielle Keiller was a collector and friend of Penrose, who had connections with Scotland. Part of Penrose's collection and Keiller's whole collection were acquired almost simultaneously by the Scottish National Gallery of Modern Art in 1995.