Question: Zulema Castro de Peña was a member of what organization that began to march in 1977 at the Plaza de Mayo in Buenos Aires?
Sentence (from "Bombing of Plaza de Mayo"): On that day, 30 aircraft from the Argentine Navy and Air Force strafed and bombed Plaza de Mayo square in Buenos Aires, in what remains to this day the largest aerial bombing ever on the Argentine mainland.
Relevant evidence: No