The ADuC SAR Eval Schematic (https://www.analog.com/media/en/technical-documentation/evaluation-documentation/151851ADuC_SAR_PCB_A3.pdf) lower left corner shows a combination of 2 OP491 stages labeled U3-E and U4-E. Furthermore there's a label "V0 = 2V1 - V2"
What is the purpose of U3-E and U4-E mentioned there ? Is that a voltage divider ? Since the OP491 is a quad-op-amp (Ux-A to Ux-D) how can there a Ux-E ?