Equation referencing

For page specific messages
For page specific messages

A few examples of equation referencing by their numbers: [Right click any mathematical equation to see its LaTeX code]

Here is a labeled equation:
with a reference to ref1:\ref{ref1},
and another numbered one with no label:
This one uses \nonumber:

Here's one using the equation environment:
and one with equation* environment:

This is a forward reference [\ref{ref2}] and another \eqref{ref2} for the
following equation:
More math:
Here is a ref inside math: \(\ref{ref2}+1\) and text after it.

x& = y_1-y_2+y_3-y_5+y_8-\dots
&& \text{by \eqref{ref1}}\\
& = y'\circ y^* && \text{(by \eqref{ref3})}\\
& = y(0) y' && \text {by Axiom 1.}

Here's a bad ref [\ref{ref4}] to a nonexistent label.

An alignment:
and a starred one: