Published by Wizards of the Coast.
Sadly, this edition is not available in PDF but 1983 Boxed Set is at RPGNow.
Though my fondness for Judge’s Guild’s Wilderlands has since eclipsed it, I still consider 1980’s The World of Greyhawk Fantasy World Setting to be the best campaign setting product TSR ever produced. I can already hear the chorus of disagreement rising in the background, as fans of Planescape and Dark Sun, Birthright and Ravenloft, even the 1983 Greyhawk boxed set prepare to show me the error of my ways. They’re welcome to try and make their case, but I’m not easily dissuaded on this point, as I’ll explain.
Read the Full Retrospective/Review at Grognardia.