Duccius[?] - inscriptions, notably a tombstone of Lucius Duccius Rufinus at York[2] (http://museums.ncl.ac.uk/archive/arma/contents/iconog/tombston/cent1/uk/york/duccius.htm)
... the formula should be understood as "either of those element(s) of the field whose square equals b2 - 4ac". In some fields, some elements have no ...