\magnification 800
\input folienfig
\hsize=5cm

\line{\rnode{twomass}{2MASS}\hfil\rnode{sdss}{SDSS}\hfil
\rnode{wise}{WISE}}
\vskip 2cm

\line{\rnode{p11}{$\oplus$}\hfil\rnode{p12}{$\oplus$}\hfil
\rnode{p13}{$\oplus$}\hfil}

\vskip 1.75cm

\line{\hfil\rnode{p21}{$\oplus$}\hfil\rnode{p22}{$\oplus$}\hfil
\rnode{p23}{$\oplus$}}

\def\relpair#1#2{$\langle \hbox{#1},\hbox{#2}\rangle$}

\vskip 1.5cm
\centerline{\Rnode{result}{\vbox{\hsize=4.5cm
\noindent\relpair{2MASS-3}{SDSS-132}\hfil\break
\relpair{SDSS-132}{WISE-54}\hfil\break
\relpair{2MASS-29}{WISE-21}\hfil\break
\relpair{WISE-21}{2MASS-3}\dots}}}

% sky flow
\psset{nodesepA=2pt,nodesepB=0pt}
\psset{linewidth=2pt,linecolor=black}
\ncline{twomass}{p11}
\ncline{twomass}{p21}
\ncline{sdss}{p12}
\ncline{sdss}{p22}
\ncline{wise}{p13}
\ncline{wise}{p23}
\naput[nrot=:U]{sky}

% result flow
\psset{linewidth=1pt}
\ncdiagg[angleA=270,armA=3cm]{->}{p11}{result}
\naput[nrot=:U]{pairs}
\ncdiagg[angleA=270,armA=3cm]{->}{p12}{result}
\ncdiagg[angleA=270,armA=3cm]{->}{p13}{result}
\ncdiagg[angleA=270]{->}{p21}{result}
\ncdiagg[angleA=270]{->}{p22}{result}
\ncdiagg[angleA=270]{->}{p23}{result}

% observed flow
\psset{linewidth=.5pt,linecolor=darkgray}
\ncline{sdss}{p11}
\ncline{wise}{p21}
\nbput[nrot=:D,npos=0.65]{cat}
\ncline{twomass}{p12}
\ncline{wise}{p22}
\ncline{twomass}{p13}
\ncline{sdss}{p23}

\bye