Whenever there exists a quasi-skew Hadamard matrix of order 4m and (4n - I, k, m - n + k) and (4n - I, u, u - n) configurations with circulant incidence matrices, then there exists an Hadamard matrix of order 4m(4n - I).
History
Citation
Jennifer Seberry Wallis, A class of Hadamard matrices, J. Combinatorial Theory, 6, (1969), 40-44.
