This collection of original papers on the special and general Theories of relativity is an unabridged translation of the 4th edition of das relativitatsprinzip, together with a revised edition of an additional paper by h...This collection of original papers on the special and general Theories of relativity is an unabridged translation of the 4th edition of das relativitatsprinzip, together with a revised edition of an additional paper by h.a.