One of the first CORE creations for Imperium Games was Milieu 0. The work was done by an international team including myself and Andy in the UK, Michael Barry (Au), Stuart Dollar (US), David Elrick (Au), Jo Grant (UK) and Joe Walsh (US). Again everything was email and we had a real 24 x 7 development environment. Andy or I would write something. Mail it out to Stuart or Joe in the US. As we went to bed they'd start commenting on it and mail it on to Michael. Michael would get up, work on it, and mail comments back to Andy and I ready for the next day.
Milieu 0 was the main sourcebook for the Milieu 0 setting and showed Referee's how to run adventures in these early days of the Third Imperium.
My contribution was Chapter 3 - The First Wave. I know this because the chapter is credited to Vur Biddaden, an anagram of David Burden ( I leave it to you who wrote which of the other chapters). As its title suggests it deals with how the Third Imperium spread out beyond Core and the roles of Scouts, the Imperial Navy, the Imperial Army, the Marines.
Again the supplement was well recieved, one player saying "these are far and away the most useful sourcebooks yet for T4".
Milieu 0 was later repackaged with the corrected First Survey data to form the hardback Milieu 0 Campaign.