Connection Between Wave Functions in the Dirac and Foldy-Wouthuysen   Representations
  The connection between wave functions in the Dirac and Foldy-Wouthuysen representations is found. When the Foldy-Wouthuysen transformation is exact, upper spinors in two representations differ only by constant factors, and lower spinors in the Foldy-Wouthuysen representation are equal to zero. 
Alexander J. Silenko