Original: Gnatt , A.L. , Cramer , P. , Fu , J. , Bushnell , D.A. and Kornberg , R.D. ( 2001 ) Structural basis of transcription : An RNA polymerase II elongation complex at 3.3 Å resolution .
Simplified: Cramer , P. , Bushnell , D.A. and Kornberg , R.D. ( 2001 ) Structural basis of transcription : RNA polymerase II at 2.8 ångstrom resolution .