 Charters produced from 928 by King Æthelstan 's scribe , " Æthelstan A " , include unusual words almost certainly copied from the Hiberno @-@ Irish poems Adelphus adelphe and Rubisca . The poems display a sophisticated knowledge of Greek and are described by Lapidge as " immensely difficult " . It is likely that they were brought by Israel from the Continent , while Adelphus adelphe was probably , and Rubisca possibly , his work . 
