I am exploring the feasibility of presenting two interacting PDF files side by side. Thus far my experiments with \usereferences have managed only to produce a lua error: .../ConTeXt/tex/texmf-context/tex/context/base/strc-ref.lua:1394: attempt to call field 'reference' (a nil value) stack traceback: .../ConTeXt/tex/texmf-context/tex/context/base/strc-ref.lua:1394: in function 'identify_outer' .../ConTeXt/tex/texmf-context/tex/context/base/strc-ref.lua:1620: in function 'identify' .../ConTeXt/tex/texmf-context/tex/context/base/strc-ref.lua:1645: in function 'valid' .../ConTeXt/tex/texmf-context/tex/context/base/strc-ref.lua:1667: in function 'doifelsereference' [\directlua]:1: in main chunk The setup-- %testA.tex \starttext text text.\reference[firstpage]{} text text.\footnote[fnote]{A note.} \stoptext %LinkTest.tex \setupinteraction[state=start] \useexternaldocument[testA.tex] \usereferences[testA.tex] \starttext \at{page}[testA.tex::firstpage] \in{note}[testA.tex::fnote] \stoptext