EINSTEIN, Albert (1879-1955). Typed letter signed (''A. Einstein'') to Daniel M. Lipkin, Princeton, 1 October 1952.

EINSTEIN, Albert (1879-1955). Typed letter signed ("A. Einstein") to Daniel M. Lipkin, Princeton, 1 October 1952.

One page, 280 x 218mm on Institute for Advanced Study letterhead with the original transmittal envelope.

Einstein offers a brief critique of a set of equations sent by his correspondent, opining that his "choice of coordinate system is quite obvious and generally known." But adds that it is only "an incomplete determination fixing only 1 of the 4 arbitrary functions." It appears to him that in developing the theory, specializing the coordinate system is not warranted.