Department of Mathematical Sciences;
University of South Africa;
Unisa;
South Africa;
Department of Mathematics (Pure and Applied);
Rhodes University;
Grahamstown;
South Africa;
Black; Hole; Linear; Perturbations; Null; Cone; Formalism; Bondi-Sachs; Formalism; Odd; Parity; Perturbations; Even; Parity; Perturbations;