.PS
lineht=0.25
boxht=0.25
boxwid=0.25
ST: down arrow
arrow right then down
box invis "RP"
arrow down
left line
X: line to ST
arrow down at X
box invis "TL"
arrow down
box invis "AU"
arrow down
box invis "AI"
arrow down lineht*2 right lineht*4 from last box .e
Y: line down lineht*6
box invis "NH, SH"
arrow down right 
arrow from X right down then down lineht*7
box invis "AB"
line down
box invis "AE"
line right lineht*4.5  down lineht*2
arrow down lineht*4
box invis "PP, LP"
arrow down
box invis "text ..."
line down
arrow from Y right down then down lineht*4.5
.PE