6 2 8 D O C . 4 1 4 C A L C U L A T I O N S AD. [28 025]. Written on the same page as the preceding document, on the verso of [28 026]. [1]Dated by the fact that it is written on the same page as the preceding document. [2]Einstein starts from De Broglie’s relation between mass and wavelength of material particles (see Einstein 1925f [Doc. 385], eq. [55]).