// Forward declarations.
-/**
+/**
* This class implements a black box preconditioner for saddle points
* systems arising from the Stokes or Navier–Stokes equations as
* specified by the papers <em>D. Silvester, A. Wathen, Fast iterative
* solution of stabilised Stokes systems part II. Using general block
- * preconditioners, SIAM J. Numer. Anal. 31:1352&ndash1367 (1994)</em>
+ * preconditioners, SIAM J. Numer. Anal. 31:1352–1367 (1994)</em>
* and <em> D. Kay, D. Loghin, A. Wathen, A preconditioner for the
* steady-state Navier–Stokes equations, SIAM
* J. Sci. Comput. 24(1):237–256 (2002)</em>, respectively.
*
+ * The preconditioner is based an approximation to the Schur
+ * complement of the block matrix. The Schur complement $S=B
+ * A_{\mathbf u}^{-1} B^T$ is approximated by a mass matrix $M_p$ on
+ * the pressure space in the case of the Stokes equations, and as a
+ * product $S^{-1} = L_p^{-1} F_p M_p^{-1}$ with pressure Laplace
+ * matrix $L_p$, pressure convection-diffusion operator $F_p$
+ * (corresponding to the sum of time derivative, convection and
+ * diffusion), and pressure mass matrix $M_p$ in the case of the
+ * Navier–Stokes equations.
+ *
* @ingroup TrilinosWrappers
* @ingroup Preconditioners
* @author Martin Kronbichler, 2008