Fourth Test of General Relativity: Preliminary Results Shapiro, Irwin I. ; Pettengill, Gordon H. ; Ash, Michael E. ; Stone, Melvin L. ; Smith, William B. ; Ingalls, Richard P. ; Brockelman, Richard A. Abstract Not Available Publication: Physical Review Letters Pub Date: May 1968 DOI: 10.1103/PhysRevLett.20.1265 Bibcode: 1968PhRvL..20.1265S