Who wrote the Undermountain adventure?

So who wrote the Undermountain adventure? Anyone know? #dnd #origins

— SlyFlourish (@SlyFlourish) June 15, 2016

@Millatron81 @SlyFlourish I wrote the UnderMountain box, and @StevenESchend edited it down so it would FIT in the box. He wrote (next tweet)

— Ed Greenwood (@TheEdVerse) June 16, 2016

@Millatron81 @SlyFlourish …the Dungeon Crawl modules. Later hc book: me for the topmost stuff and uberview, Eric Boyd, and @seankreynolds

— Ed Greenwood (@TheEdVerse) June 16, 2016