Krassimir Atanasov Sotir Sotirov Multylayer perceptron representation by index matrices with elements in a fixed interval. 1-3 2020 ECCTD https://doi.org/10.1109/ECCTD49232.2020.9218374 conf/ecctd/2020 db/conf/ecctd/ecctd2020.html#AtanasovS20