Stephen P. Humphries Nathan Nicholson Difference Sets Disjoint from a Subgroup II: Groups of Order 4p<sup>2</sup>. 2333-2349 2021 37 Graphs Comb. 6 https://doi.org/10.1007/s00373-021-02355-0 db/journals/gc/gc37.html#HumphriesN21