tt></b></dt>
	<dd> Returns the determinant of the square
  matrix <tt>a</tt>.</dd>
 <dt><b><tt>diff(a,b1,c1,b2,c2,...,bn,cn)</tt></b></dt>
	<dd> Gives the mixed partial
  derivative of <tt>a</tt> with respect to each <tt>bi</tt>, <tt>ci</tt> times.
  For brevity, <tt>diff(a,b,1)</tt> may be represented by <tt>
    diff(a,b)</tt>.  <tt>'diff(...)</tt> represents the unevaluated
  derivative, useful in specifying a differential equation.</dd>
 <dt><b><tt>eigenvalues(a)</tt></b></dt>
	<dd> Returns two lists, t