Hell Notes: Celebrating 20 Years of Hellboy – Multiversity Comics
Hellboy And The B.P.R.D.: Night Of The Cyclops ~ Hellboy Gets To Play Tragic Greek Hero [Spoilery Comic Review] - That Hashtag Show
Mike Mignola - Hellboy with horns, in Milos K's Mike Mignola Comic Art Gallery Room
Does Hellboy break his horns all the time to keep it from growing? Why does he keep doing it? Is it because his horns represent the end of the world? - Quora
Hellboy w/ Horns, in D J's Mignola Comic Art Gallery Room