Papers on Difference Sets

On cyclic difference sets, Len Baumert and Dan Gordon, 2003.
This paper gives a survey of results for cyclic difference sets, and lists open parameters with k<300.

The Prime Power Conjecture is True for n < 2,000,000, Dan Gordon,
Electronic Journal of Mathematics, 1 (1994), Paper R6.

Some Restrictions on Orders of Abelian Planar Difference Sets
Journal of Combinatorial Mathematics and Combinatorial Computing, 29 (1999), pp. 241-246.
This paper gives new numbers which cannot divide the order of an abelian planar difference set.