Computers & mathematics with applications (1987) 74 (2017): 1059–1075. doi:10.1016/j.camwa.2017.04.033 info:cnr-pdr/source/autori:M. Porcelli, V. Simoncini, and M. Stoll/titolo:Preconditioning PDE-constrained optimization with L^1-sparsity and control constraints/doi:10.1016%2Fj.camwa.2017.04.033/rivista:Computers & mathematics with applications (1987)/anno:2017/pagina_da:1059/pagina_a:1075/intervallo_pagine:1059–1075/volume:74