- Astronomical instruments1
- Astronomy, Ancient1
- Astronomy--Popular works1
- Attila, -4531
- Aubertus, de Galardone1
- Audiore, Antonio1
- Augsburg Confession1
- Augustus, Emperor of Rome, 63 B.C.-14 A.D.1
- Aurispa, Giovanni, approximately 1376-14591
- Austria--Lambach (Upper Austria)1
- Authors, Latin1
- Autograph albums1
- Aveiro, Gabriel de Lencastre, Duque de, 1667-17451
- Azar, Menaḥem ben Natan1
- Baglioni, Niccolò1
- Baldi, Filippo1
- Baldini, Antonio1
- Baldo, Antonio di1
- Baldo, Vestro di1
- Balducci, Domenico1