Complex sentence: Joining Einstein, Bertrand Russell and eight other leading scientists and intellectuals, he signed the Russell-Einstein Manifesto issued July 9,1955 and the Mainau Declaration of July 15,1955, signed by 52 Nobel Prize laureates.
Split into simpler sentences: Joining Einstein, Bertrand Russell and eight other leading scientists and intellectuals, he signed the Russell-Einstein Manifesto issued July 9,1955. He also supported the Mainau Declaration of July 15,1955, signed by 52 Nobel Prize laureates.