Authors will probably not cross reference every equation in
text. When a numbered equation needs to be referred to in text
by its number, the label{tag} and ref{tag}
commands should be used. The label command is used within
the equation or the eqnarray line to be referenced.
input:output:
begin{equation}
SPM_quotx^2 + y^2 + z^2 = - t"
label{schroedinger}
end{equation}
... It follows from Eq. (ref{schroedinger}) that this is the case...
... It follows from Eq. (1) that this is the case...
Please note the parentheses surrounding the command. They are necessary for proper output. You can also label individual lines in an eqnarray. Numbers produced with eqnum can also be cross referenced; just follow the eqnum command with a label command. See section F. Footnotes and References for further information.
