Swanson, C.N., Correll, Jr., B. and Ho, R.W. 2016. Enumeration of Parallelograms in Permutation Matrices for Improved Bounds on the Density of Costas Arrays. The Electronic Journal of Combinatorics. 23, 1 (Mar. 2016), #P1.44. DOI:https://doi.org/10.37236/5610.