Appendix A: Mathematical background 357 A.1 Domains for sequences and functions 357 A.2 Classes of sequences and functions 358 A.2.1 Functions on the domain Rd 359 A.2.2 Sequences on the domain Zd 359 A.2.3 Classes of functions on the domain Sd 1 360 A.2.4 Classes of sequences on the domain Zd N, where N = (n[1]; : : : ; n[d]) 360 A.3 Matrix algebra 360 A.3.1 The spectral decomposition theorem 360 A.3.2 Moore-Penrose generalized inverse 361 A.3.3 Orthogonal projection matrices 362 A.3.4 Partitioned matrices 363 A.3.5 Schur product 364 A.3.6 Woodbury formula for a matrix inverse 364 A.3.7 Quadratic forms 365 A.3.8 Toeplitz and circulant matrices 366 A.3.9 Tensor product matrices 367 A.3.