The next step is to learn about "diacriticals", which
is a big word for funny marks on symbols, like
a bar over something ($x bar$), or a tilde or hat on
something ($x tilde ,~a hat$), or perhaps a dot
or dotdot ($T dot ,~U dotdot$), or even an
underlining like $abc under$.
These are all easy. Each funny character
has a name, and all you have to do is put the name
after the thing you want the character on.
x tilde makes $x tilde$ (notice that we spell tilde)
u dotdot makes $u dotdot$ (looks ugly on a terminal)
Except for "bar" and "under", these are almost always
attached to just a single letter.
If you want to put a bar over something longer, like
${2 pi +1} bar$, simply enclose the thing in braces:
Modify "Example" to produce output that looks like this,
Let $x bar$, $y bar$, and $z bar$ be the components of $pi bar$.
Let ${alpha +1} bar$ be the mean value of $alpha hat$.
Let x bar, y bar, and z bar be the components of pi bar.
Let alpha +1 bar be the mean value of alpha hat.
#once neqn Ref | nroff >X1 &
#once neqn message Ref | nroff -T$term %s/tinyms -
Don't forget to set delimiters at the beginning,
and get the spaces right around the dollar signs.