Complex sentence: While in Stuttgart, Cassidy began his full-scale biography of Heisenberg, and he collaborated with Karl von Meyenn on the second volume of the scientific correspondence of Wolfgang Pauli, covering the 1930s.
Split into simpler sentences: While in Stuttgart, Cassidy began his full-scale biography of Heisenberg. He also collaborated with Karl von Meyenn on the second volume of the scientific correspondence of Wolfgang Pauli, covering the 1930s.