The two Wileman texts (1980, 1993) have provided (and updated) a typology for the realism continuum that has been
adopted by several other authors (e.g., Pettersson, 1993; Braden, 1994). Knowlton (1966) proposed that images be
categorized for purposes of study and research. His categorization scheme was based primarily on degrees of realism.
Levie and Lentz (1982), while concentrating on the effects of illustration on text, digressed to discuss providing additional
pictorial information