4.3BSD-Tahoe/usr/lib/learn/eqn/L3.1d

#once #create message
.ND
.PP
There is one special construction with subscripts
and superscripts that you have to be aware of, although
it almost always does what you want automatically.
When something has both a subscript and a superscript,
it is usually printed as
.EQ
x sub i sup j
.EN
instead of
.EQ
{x sub i} sup j
.EN
To produce this effect, with the superscript _____above the
subscript instead of to the right, you have to type
the subscript ______before the superscript, like this:

   .EQ
   x sub i sup j
   .EN

That's all there is to it.

Modify "Example" to produce the following output, then type "ready".
.pl 1
#once #create Ref
.LP
.EQ
x sub ij sup kmn = y sub i sub j
.EN
.pl 1
#once #create Example
.LP
.EQ
xxx
.EN
.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
3.1e 10
3.2d 5