The demon Buer appears in the grimoires Book of Incantations, The Discoverie of Witchcraft, The Grand Grimoire, Pseudomonarchia Daemonum, The Lesser Key of Solomon, and Dictionnaire Infernal
From The Lesser Key of Solomon, Crowley/Mathers edition:
The Tenth Spirit is Buer, a Great President. He appeareth in Sagittary, and that is his shape when the Sun is there. He teaches Philosophy, both Moral and Natural, and the Logic Art, and also the Virtues of all Herbs and Plants. He healeth all distempers in man, and giveth good Familiars. He governeth 50 Legions of Spirits, and his Character of obedience is this, which thou must wear when thou callest him forth unto appearance.
Timeline of related events
1536Publication of De praestigiis daemonum (lists this demon)
1584Publication of The Discoverie of Witchcraft (lists this demon)
1641Publication of the Lesser Key of Solomon (lists this demon)