The origin of Twenty20 Cricket,
Dr George Christo
s 1997

media release, 5 Jan 2009

article in the West Australian Newspaper, 6 Jan. 2009
[Dr Christos was in constant contact with the ICC and the EWCB 
during the period 1996-2000 about the one-day cricket rain rule, 
so it is preposterous to suggest, as the ICC does in this article, 
that they receive lots of letters and do not remember 
the letter of 2 May 1997 from Dr Christos.]

The idea of 20/20 cricket was actually put forward to the ICC and the EWCB in a letter dated 2 May 1997 by Dr George Christos, a mathematician, at Curtin University, Perth, Western  Australia.  His letter, not only puts forward the idea of 20/20 cricket, but clearly outlines why it will be a huge success. Dr Christos, came up with this idea while working on a rain-rule for one-day 50-over cricket (called the ‘wicket-averaging method’), which was considered by the ICC, but who chose to stay with the Duckworth-Lewis method. Dr Christos was motivated to come up with a game (20/20 cricket) in which there would be no need to use the Duckworth-Lewis method.

original letter to the ICC (copy to EWCB) in May 1997

reply from ICC to this letter, May 1997

reply from the EWCB, June 1997

In a recent letter to the ICC, Dr George Christos writes to seek recognition of his intellectual property, Dec. 2008
page 1 of letter 2008
page 2 of letter 2008
page 3 of letter 2008

link to article published in "The Cricketer", December 1998 regarding his 'wicket-averaging method' rain-rule proposed to the ICC, which is simpler to understand and play with, than the Duckworth-Lewis method, and is cost free, unlike the Duckworth-Lewis method, which requires software, updates to tables, and personnel.
page 1
page 2

link to correspondence in "The Cricketer", January 1999, regarding the Duckworth-Lewis system.
page 1