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McGrank, Lawrence (1981). "Norman crusaders and the Catalan reconquest: Robert Burdet and the Principality of Tarragona 1129-55". Journal of Medieval History. 7 (1): 67–82. doi:10.1016/0304-4181(81)90036-1.
Estonian Theological Society in Exile (April 1956). "Charisteria Iohanni Kõpp octogenario oblata. 304 pp. Stockholm, 1954. $5.00. (Papers of the Estonian Theological Society in Exile, No. 7.) (May be obtained from the Bookstore, Chicago Lutheran Theological Seminary, Maywood, Ill.)". Theology Today. 13 (1): 129. doi:10.1177/004057365601300124. ISSN0040-5736. S2CID220990258.
Estonian Theological Society in Exile (April 1956). "Charisteria Iohanni Kõpp octogenario oblata. 304 pp. Stockholm, 1954. $5.00. (Papers of the Estonian Theological Society in Exile, No. 7.) (May be obtained from the Bookstore, Chicago Lutheran Theological Seminary, Maywood, Ill.)". Theology Today. 13 (1): 129. doi:10.1177/004057365601300124. ISSN0040-5736. S2CID220990258.
Estonian Theological Society in Exile (April 1956). "Charisteria Iohanni Kõpp octogenario oblata. 304 pp. Stockholm, 1954. $5.00. (Papers of the Estonian Theological Society in Exile, No. 7.) (May be obtained from the Bookstore, Chicago Lutheran Theological Seminary, Maywood, Ill.)". Theology Today. 13 (1): 129. doi:10.1177/004057365601300124. ISSN0040-5736. S2CID220990258.