| v11 c12 c13 c14 |         |  1  r12 r13 r14 |
    | c21 v22 c23 c24 |         | r21  1  r23 r24 |
M = | c31 c32 v33 c34 |     C = | r31 r32  1  r34 |
    | c41 c42 c43 v44 |         | r41 r42 r43  1  |

    | s11  0   0   0  |
    |  0  s22  0   0  |
D = |  0   0  s33  0  |
    |  0   0   0  s44 |

M = D*C*D