J. Cowles and T. Bailey. Several Versions of Ackermann's Function. Dept. of Computer Science, University of Wyoming, Laramie, WY. 1988-09-30 [2009-04-17]. (原始内容存档于2008-10-04).
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I. N. Galidakis. Mathematics. 2003 [2009-04-17]. (原始内容存档于2009-04-20).
J. Cowles and T. Bailey. Several Versions of Ackermann's Function. Dept. of Computer Science, University of Wyoming, Laramie, WY. 1988-09-30 [2009-04-17]. (原始内容存档于2008-10-04).