Three-banked ("trireme") dromons are described in a 10th-century work dedicated to the "parakoimōmenos" Basil Lekapenos. However, this treatise, which survives only in fragments, draws heavily upon references on the appearance and construction of a classical Greek trireme, and must therefore be used with care when trying to apply it to the warships of the middle Byzantine period. The existence of trireme vessels is, however, attested in the Fatimid navy in the 11th and 12th centuries, and references made by Leo VI to large Arab ships in the 10th century may also indicate trireme galleys.