I’m going on memory here, without looking it up for confirmation, but I believe they were mentioned in Field Manual: Crusader Clan, Warden Clan, and there was a specific write-up in Interstellar Players 2. I don’t believe it’s ever been shown on a map, but they have been given a good stellar cartographic description. If memory serves, they are 50 light years from the Pentagon, and 30 light years from the Exodus Road (Invasion Route), or Kerensky’s Exodus Route. I can’t remember right now.