[http://www.nga.gov/content/ngaweb/research/casva/research-projects.html A Project of the National Gallery of Art, Center for Advanced Study in the Visual Arts ]
Shouldn't captions indicate where the alcove is when it is not clear from the image or a letter is keyed to it? eg. fig. 5
shouldn't the Downing image be inscribed? should discuss differences with keyed images that are being identified as inscribed.