From the Berlin "Entwurf" Field Equations to the Einstein Tensor II:   November 1915 until March 1916
  I discuss Einstein's path-breaking November 1915 General Relativity papers. I show that Einstein's field equations of November 25, 1915 with an additional term on the right hand side involving the trace of the energy-momentum tensor appear to have sprung from his first November 1915 paper: the November 4, 1915 equations. Second paper among three papers. 
Galina Weinstein
physics.hist-ph