1. Definitions and Some Preliminary Results2. L-Structures3. The Commutation Matrix4. Symmetry: The Duplication Matrix5. Lower Triangularity: The Elimination Matrix6. Skew-Symmetry and Strict Lower Triangularity7. Diagonality8.

Other L-Structures9. Jacobians10. Application of the Duplication Matrix to the Normal Distribution11. Implicit versus Explicit Constraints12. Matrix Equations13. Treatments of Diagonality in the Simultaneous Equations System14. Other Applications15. Index.