 Complete the following phrase:  Martíns first exhibition came in 1949 at the Cristal Bookstore just off the Alameda Central in Mexico City, in which she demonstrated her works in painting and drawing. She then became a member of the Taller de Gráfica Popular focusing on printmaking with political and social themes such as images of workers, indigenous people, prisoners and works supporting the Cuban Revolution. In the early 1950s, she met Diego Rivera, who invited her to collaborate on mural projects at the Teatro de Insurgentes and The Olympic Stadium of the Ciudad Universitaria. From 1955 to 1960, she exhibited her work in Europe Warsaw, Paris, Ljubljana, Stavropol, Moscow and Prague, Beijing and San Antonio, Texas. The 