I spent several years as the History of the Imperium Working Group (HIWG)'s Gushemege sector analyst, naming all the worlds in the sector (with some help from Leighton Piper and later David Lai), and beginning to flesh out its history. I self published an A5 guide to the sector to the same format as the GDW Spinward Marches supplement, as well as releasing all the files to the HIWG. You can now find the data populating several web sites and astrogarphy programmes around the web - the best of which I've linked to below. When Milieu 0 was released by Imperium Games they totally ignored the HIWG work and gave all the worlds in every sector new names. But seeing as no-one ever really bought into the IG vision and Milieu ) almost all web references are still to the HIWG names. Interesting debate as to which are canon and which will be reflected by new GURPS and T20 material.
Good versions of the sector are:
During 2019 I revisited all my old Gushemege material and assembled it into a 200 page Gushemege Sector Sourcebook which will hopefully see light of day later in 2020.