To use this program, you will need to obtain a licence and become a registered user of DIRDIF. Please contact Paul Beurskens (NOT Louis Farrugia!) for further details (email address below).
The official DIRDIF website: http://www.sci.kun.nl/xtal/dirdif/software/dirdif.html
Contact address : Professor Dr Paul T. Beurskens, Laboratorium voor Kristallografie, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen THE NETHERLANDS (email: ptb@sci.kun.nl)