“…The most essential property of these successful sparse arrays is that, given N sensors, the difference coarrays of these arrays have O (N 2 ) elements, which allows them to identify D = O (N 2 ) sources using N sensors. In particular, therefore, D N is possible as demonstrated amply in [1][2][3][16][17][18][19]21,[28][29][30][31][32]36,40,53,57,58,61,63,64,67,68,70,71,[74][75][76][77]93,94,96,98,107,108].…”