There are hundreds, maybe over a thousand published sources for the Second Anglo-Boer War ranging from contemporary accounts and diaries, regimental and war histories, picture books to the modern histories and accounts. Other items not directly associated with the war such as maps and the wonderful The Encyclopaedia of South African Post Offices and Postal Agencies, Hale & Putzel, Cape Town, 1986 are very useful too.
In creating The Register I have consulted over 540 different sources which are listed here. In the past few days I stumbled across a new source made available through the internet: The Tablet, The International Catholic News Weekly. In The Archive section are OCR copies from 1840. In this paper can be found obituaries or less formal death notices about many Roman Catholic soldiers. I found it most useful for WW1 in finding soldiers who served in the ABW only to die during WW1.
The best connection was Father and Major Simon Stock Knapp, DSO, MC who died of wounds in 1917. The Tablet revealed he had served in the ABW. The only Knapp in the Army Chaplains medal roll is Father F Knapp; are they the same? A quick Google bought up this wonderful history of Father F[rank]/Simon Stock Knapp which proves the gallant Father so beloved by his soldiers in WW1 was Father F Knapp from the ABW medal rolls.
This connection would have been hard to make starting from "Father F Knapp", but now we know, and another character of the ABW is bought to life.