Some poking around suggests that changing the iframe URL in opac/parts/record/summaryplus.tt2 so that it uses "Options=N" rather than "Options=Y" will remove the close button from the embedded content.
Some poking around suggests that changing the iframe URL in opac/parts/ record/ summaryplus. tt2 so that it uses "Options=N" rather than "Options=Y" will remove the close button from the embedded content.