"One of the turning-points in the development of relativity theory. Einstein had realized that he could proceed no further without expert mathematical help, and called upon his friend Michael Grossmann to supply it. Using the tensor calculus, the two were able to write a mathematical representation of gravitation representing a tenfold expansion from Newton's single gravitational potential - yet Einstein, with the problems of physical interpretation still unresolved, backed away from the necessity of considering ten corresponding field equations" -Norman 693.
FIRST EDITION, OFFPRINT, of Einstein’s breakthrough work on general relativity: the famous “Entwurf” paper.
“In this book, Einstein and Grossman investigated curved space and curved time as they relate to a theory of gravity. They presented virtually all the elements of the general theory of relativity with the exception of one striking omission: gravitational field equations that were not generally covariant. Einstein soon reconciled himself to this lack of general covariance through the ‘hole argument,’ which sought to establish that generally covariant gravitational field equations would be physically uninteresting. Einstein did not adopt the gravitational field equations until late in 1915 in his final formulations of the general theory. Here, Einstein contributed the physics and Grossman the mathematics” (Calaprice, The Einstein Almanac, 40). Weil 59a.
Offprint from Zeitschrift für Mathematik und Physik, volume 62. Leipzig and Berlin: Teubner, 1913. Octavo, original wrappers; custom box. Minor crease to rear wrapper. An outstanding copy, very rare in such good condition.