In the 1950's and 1960's John Ciardi, then at Rutgers University,
translated into verse all three sections of Dante's Divine Comedy. 
These translations were published by Penguin under the Mentor name as
three separate books titled The Inferno, The Purgatorio, and The
Paradiso.  These books were very well received and reviewed, and have
subsequently been reprinted many times since first being published -
most recently in 1993.  On the cover of all three books there is a
symmetrical, water-colour artwork depicting the artist's
interpretation of Dante's poems.  There isn't any credit given in
these books for the cover art, and I haven't been able to find any
mention or reference to these artwoks anywhere else.  Could you tell
me who the artist is, the titles of the works, and where, if possible,
prints can be had?