Offprint booklet of Silberstein's paper 'On Einstein's Gravitational Field Equations,' from the Philosophical Magazine (November 1937), 5.5 x 8.5, ten pages, signed and inscribed on the front wrapper in fountain pen to his son, "To dear George, in remembrance of the snowstormy night of Valentine, 14 Feb. 1938, from Ludwik." The paper begins: "The purpose of Part I. of this paper is to prove that Einstein's field-equations in empty space (Tik=0) do not admit any radially (spherically) symmetrical solutions varying in time; in other words, that the solutions of this kind are necessarily statical." A footnote states: "I have communicated this result, with its derivation, to Dr. Einstein in a private letter of December 1933." In fine condition, with minor creases to wrappers, and pencil annotations to rear wrapper. From the collection of physicist Ludwik Siberstein.