One of the core assumptions the authors of the „White Book” decided to base their work on was fundamental usage of sources available over the Internet, both for research and analytical purposes. And such is the case today. In order to complete the lexicon in a form users are able to access now many years long effort of perusing, scanning and analyzing tens of thousands of net pages, mainly in Polish, but also in German, Russian, English, Ukrainian, Belarusians, Lithuanian, Latvian, Czech, etc., was required and undertaken. As a result each of the particular biographies contains references to scores of sources — hyperlinks to other pages — each with its own access availability date.

The Internet resources however — and references to c. 9,750 different links are used in the Book — are „fleeting” in nature, undergo frequent modifications, appear and then disappear, so the authors of the „White Book” cannot be held responsible for their changes/availability over time.

The other pool of sources the „White Book” owes its range and accuracy to are publically available lexicons published over the last dozens of years, mainly in Poland. Among them the most important ones are:

• Dzwonkowski Roman, SAC — „Lexicon of Polish clergy repressed in USSR in 1939‑1988”, ed. Science Society KUL, 2003, Lublin
• Dzwonkowski Roman, SAC — „Fate of the Catholic clergy in USSR 1917‑39. Martyrology”, ed. Science Society KUL, 2003, Lublin
• editor Fr Grzebień Louis, SI — „Jesuits on Polish and Lithuanian territory knowledge encyclopedia, 1564‑1995”, WAM Printing House, Cracow 1996
• Fr Grzybowski Nicholas Marian — „Płock diocese clergy martyrology during II World War 1939‑1945”, Włocławek–Płock 2002
• Fr Hanich Andrew — „Opole Silesia clergy's martyrology during II World War”, Opole 2009
• Jacewicz Victor, Woś John — „Martyrology of the Polish Roman Catholic clergy under nazi occupation in 1939‑1945”, vol. I‑V, Warsaw Theological Academy, 1977‑1981
• Janecki Lukas — „Biographical–bibliographical dictionary of Polish Conventual Franciscan Fathers murdered and tragically dead in 1939‑45”, Franciscan Fathers' Publishing House, Niepokalanów, 2016
• Fr Krahel Thaddeus — „Vilnius archdiocese clergy martyrology 1939‑1945”, Białystok, 2017
• collective work edited by Myszor George — „Lexicon of the clergy vicimised in prl in 1945‑1989”, Warsaw, 2002
• Pawłowiczowa Mary (ed.), Fr Krętosz Joseph (ed.) — „Biographical lexicon of Lviv Roman Catholic Metropoly clergy victims of the II World War 1939‑1945”, Holy Cross Publishing, Opole, 2007
• Prakh Bogdan — „Clergy of Przemyśl Eparchy and Apostolic Exarchate of Lemkivshchyna” (Ukr. „Греко–католицьке духовенство Перемиської єпархії та Апостольської адміністрації Лемківщини”), Ukrainian Catholic University Publishing House, Lviv 2015
• Fr Szołdrski Vladislaus CSSR — „A martyrology of Polish clergy under German occupation, 1939‑45”, Rome 1965

Finally authors are indebted to dozens, hundreds of correspondents who contributed countless data, memoirs, recollections, including photos, without which the „White Book” would not have become what it really is — one the of the largest lexicons not only over the net but in general, a testimony to the martyrdom of thousands of priests, monks and nuns who, by their sacrifice, laid foundations for the world we are living in today and forging our individual paths towards God and eternity.