S. S. Wagstaff, Jr.. The Period of the Bell Exponential Integers Modulo a Prime. In W. Gautschi, editor, Mathematics of Computation 1943-1993: A Half-Century of Computational Mathematics, Proceedings of Symposia in Applied Mathematics, Volume 48, pages 595-598. 1994.
S. S. Wagstaff, Jr. and D. Shanks. 48 More Solutions of Martin Davis's Quaternary Quartic Equation. Mathematics of Computation, 64:1717-1731, 1995.