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+#once #create message
+.ND
+.tr %$
+.EQ
+delim $$
+.EN
+.LP
+The next construction we're going to look at
+is one for putting things above and below other
+things, in a rather specialized way.
+For example, if you want something like
+.EQ
+sum from i to j
+.EN
+you type
+  .EQ
+  sum from i to j
+  .EN
+The words "from" and "to" are more magic, like
+sub or sup or over.  The "from" part is centered
+under the main piece; the "to" part is centered
+above it.
+As a warmup, modify "Example" so it produces
+output that looks like the following, then type
+ready.
+.pl 1
+#once #create Ref
+.EQ
+delim $$
+.EN
+.LP
+Let $Q( pi )$ be $sum from {i= pi sub 1} to {i= pi sub 2} x sub i$.
+.pl 1
+#once #create Example
+.EQ
+delim $$
+.EN
+.LP
+.pl 1
+#
+#once neqn Ref | nroff >X1 &
+#once neqn message Ref | nroff -T$term %s/tinyms -
+#user
+neqn Example | nroff >X2
+#cmp X1 X2
+#log
+#next
+7.1b 10