I also learned the 2 parter, “The Other Brothers Elric” came from a light novel, “The Land of Sand”, but not written by it’s original author, also 2003’s episode 37, “The Flame Alchemist, The Bachelor Lieutenant, and the Mystery of Warehouse 13”, came from the same novel as well. And I’ve noticed the 2003 episode, “Fullmetal vs Flame”, is from bonus chapters, “Dog of the Military?” and “The Military Festival”. I’ll let you decide this one, along with the Brotherhood OVAs.