The demon Barbatos appears in the grimoires Book of Incantations, The Discoverie of Witchcraft, The Grand Grimoire, The Book of Oberon, Pseudomonarchia Daemonum, The Lesser Key of Solomon, and Dictionnaire Infernal
From The Lesser Key of Solomon, Crowley/Mathers edition:
The Eighth Spirit is Barbatos. He is a Great Duke, and appeareth when the Sun is in Sagittary, with four noble Kings and their companies of great troops. He giveth understanding of the singing of Birds, and of the Voices of other creatures, such as the barking of Dogs. He breaketh the Hidden Treasures open that have been laid by the Enchantments of Magicians. He is of the Order of Virtues, of which some part he retaineth still; and he knoweth all things Past, and to Come, and conciliateth Friends and those that be in Power. He ruleth over 30 Legions of Spirits. His Seal of Obedience is this, the which wear before thee as aforesaid.
Timeline of related events
1536Publication of De praestigiis daemonum (lists this demon)
1577Book of Oberon completed (lists this demon)
1584Publication of The Discoverie of Witchcraft (lists this demon)
1641Publication of the Lesser Key of Solomon (lists this demon)