You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Muammar_Gaddafi

Context:
After Nasser died in November 1970, his successor, Anwar Sadat, suggested that rather than a unified state, they create a political federation, implemented in April 1971; in doing so, Egypt, Syria and Sudan got large grants of Libyan oil money. In February 1972, Gaddafi and Sadat signed an unofficial charter of merger, but it was never implemented as relations broke down the following year. Sadat became increasingly wary of Libya's radical direction, and the September 1973 deadline for implementing the Federation passed by with no action taken.

Question:
In what year was the merger charter signed?

1972