O'Farrell, F. (1987). Is there a history of to be? Gregorianum, 68(3/4), 671-703.
Cita Chicago Style (17a ed.)O'Farrell, Frank. "Is There a History of to Be?" Gregorianum 68, no. 3/4 (1987): 671-703.
Cita MLA (8a ed.)O'Farrell, Frank. "Is There a History of to Be?" Gregorianum, vol. 68, no. 3/4, 1987, pp. 671-703.
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