6 2 8 D O C . 4 3 4 C A L C U L A T I O N 434. Calculation [Berlin, between 14 March and 19 March 1929][1] . AD. [73 287]. On the verso of Abs. 1038. Sotheby’s Auction Catalog 3, 1986, lot 190, p. 90. [1] Dated by the date of Abs. 935 and 1038, and by the fact that Einstein also sent a copy of Doc. 435 enclosed with the latter.    hg    hg   , +   –  hg   –  hg   , h       –   hg   ,  x  hg  hg      + = hg  , hg      |  + hg  , hg      |   + 0 g  , g      g      h  + + = 0 g  , g      g      h  + + = h   g        g      –   g      – +   g      h (   – g      g  ) = 0 +