  Weyl is here referring to his three important papers, which appeared  in 1929—the same year in which he had published his detailed  critique of Cartan’s method—in which he investigates the  adaptation of Dirac’s theory of the special relativistic electron to  the theory of general relativity, and where he develops the  tetrad or Vierbein formalism for the representation of local two-component spinor structures on Lorentz  manifolds. 