D. Thompson, and C. Wilson-Hodge. (2022)cite arxiv:2210.12875Comment: 36 pages, 13 figures. To appear in "Handbook of X-ray and Gamma-ray Astrophysics" by Springer - Editors in chief: C. Bambi and A. Santangelo.
D. Hogg. (1999)cite arxiv:astro-ph/9905116Comment: This short and purely pedagogical text is not submitted anywhere but here. Errors reported to the author will be rewarded with gratitude and acknowledgements.