Papers are at the Armagh Observatory, Armagh, Northern Ireland.
Arny, Thomas, “The Star Makers: a History of the Theories of Stellar Structure and Evolution,” Vistas in Astronomy 33, 2, 211-33 (1990).
Bailey, M.E., S. V. M. Clube, & W. M. Napier, The Origin of Comets (Pergamon Press, Oxford, UK, 1990).
Bennett, J.A., Church, State, and Astronomy in Ireland: 200 Years of Armagh Observatory (Armagh Observatory, Armagh in association with the Institute of Irish Studies, the Queen’s University of Belfast, 1990).
Butler, C.J., A Short History of Armagh Observatory
De Groot, Mart, “Armagh Observatory: 200 Years of Irish Excellence,” Astronomy Now 4, 56-58 (1990).
De Groot, Mart, “Ernst Julius Öpik, 1893 - 1985. Reflections on the Life, Works and Personality of Estonia’s Greatest Astronomer.,” International Scientific Conference Devoted to the 200th Anniversary of F.G.W. Struve and J.H. Mädler and the 100th Anniversary of E. J. Öpik, 11-14 (1994).
de Vermond, Mary, “E. Öpik—Composer,” Irish Astr. Jour. Supp. 10, 82-86 (1972).
Eelsalu, Heino, “The Rise and Fall of Small Astronomical Observatories: A Case Study Dorpat/Tartu Observatory,” Journal of Astronomical History & Heritage 2, 111-23 (1999).
Glaessner, M.F., J.H. Shergold & C. Teichert, “Armin Alexander Öpik 1898-1983,” Australian Academy of Science, Biographical Memoirs of Deceased Fellows [brother]
Helin, E.F., “Professor Ernst Opik and his Asteroid 2099 Opik,” Irish Astronomical Journal 17, 428-31 (1986).
“Lembit and His Very Cheeky family,” London Evening Standard 14 April 2007.
McFarland, J. & D. Asher, “The Meteor Work of Ernst Opik at Armagh Observatory,” in D.J. Asher, A.A. Christou, P. Atreya, & G. Barentsen, eds., Proceedings of the International Meteor Conference, Armagh, Northern Ireland, 16-19 September, 2010 (International Meteor Organization, 2011), pp. 67-72.
Muursepp, Peeter & Raimund Preem, “Ernst Öpik and the Perseid Shower,” Sky & Telescope 36, 376 (1968).
Öpik, U. [son], “Reminiscences of Ernst Öpik,” International Scientific Conference Devoted to the 200th Anniversary of F.G.W. Struve and J.H. Mädler and the 100th Anniversary of E. J. Öpik p. 16.
Pustylnik, I., “E. Öpik and the Tartu School of Astrophysics and Stellar Astronomy (1922 - 1945).,”