Zulema Castro de Peña was a member of what organization that began to march in 1977 at the Plaza de Mayo in Buenos Aires?
Mothers of the Plaza de Mayo: The Mothers of the Plaza de Mayo (Spanish: "Asociación Madres de Plaza de Mayo" ) is an association of Argentine mothers whose children "disappeared" during the state terrorism of the military dictatorship, between 1976 and 1983. Mothers of the Plaza de Mayo:  They organized while trying to learn what had happened to their children, and began to march in 1977 at the Plaza de Mayo in Buenos Aires, in front of the Casa Rosada presidential palace, in public defiance of the government's state terrorism intended to silence all opposition.
i don't know