How to cite use of grade

O. S. Smart, T. O. Womack, A. Sharff, C. Flensburg, 
P. Keller, W. Paciorek, C. Vonrhein, and G. Bricogne.
(2011) grade, version] /?????/.
 Cambridge, United Kingdom, Global Phasing Ltd.,
grade -h
   author="Smart, O. S. and  Womack, T. O. and Sharff, A. and Flensburg, C. and Keller, P. and
           Paciorek,  W. and Vonrhein, C. and Bricogne, G.",
   title="grade, version 1.1.1",

Page by Oliver Smart and Tom Womack original version 23 January 2011. Address problems, corrections and clarifications to