Grilo, J.; Franca, J.E.: 'Four-quadrant multiplier combining sigma-delta and multirate processing techniques', Electronics Letters, 1991, 27, (23), p. 2146-2148, DOI: 10.1049/el:19911329
IET Digital Library, https://digital-library.theiet.org/;jsessionid=t9vlw39tf290.x-iet-live-01content/journals/10.1049/el_19911329