This document shows an example of the use of the subeqnarray environment. Here is one:
\begin{subeqnarray} \slabel{eq0} x & = & a \times b \\ \slabel{eq1} & = & z + t\\ \slabel{eq2} & = & z + t \end{subeqnarray}
The first equation is number [*], the last is [*]. The equation as a whole can be referred to as equation [*].

To show that equation numbers behave normally, here's an eqnarray environment.

x = a×b (1)
  = z + t (2)
  = z + t (3)

These are equations [*], [*] and [*].