Original: The Treaty of Berlin was the final act of the Congress of Berlin (June 13-July 13, 1878), by which the United Kingdom, Austria-Hungary, France, Germany, Italy, Russia and the Ottoman Empire under Sultan Hamid revised the Treaty of San Stefano signed on March 3 of the same year.
Simplified: The Treaty of Berlin was a part of the Congress of Berlin (June 13-July 13, 1878). In it, the United Kingdom, Austria-Hungary, France, Germany, Italy, Russia and the Ottoman Empire wrote the Treaty of San Stefano.