Let be a planar Abelian Difference Set and be any Divisor of . Then is a numerical multiplier of , where a multiplier is defined as an automorphism of which takes to a translation of itself for some . If is of the form for relatively prime to the order of , then is called a numerical multiplier.
Gordon, D. M. ``The Prime Power Conjecture is True for .'' Electronic J. Combinatorics 1, R6 1-7, 1994.