Source: https://www.researchgate.net/profile/Noureddine-Djedi/publication/239735667_Estimation_Spectrale_d'un_Signal_Compose_de_Sinusoides_par_le_Reseau_de_Hopfield/links/55fbe31808aec948c4afb6ba/Estimation-Spectrale-dun-Signal-Compose-de-Sinusoides-par-le-Reseau-de-Hopfield.pdf