After that, experiments with ultracold neutrons (UCN) took over. It started in 1980 with an experiment at the Leningrad Nuclear Physics Institute [ ru ] (LNPI) obtaining a limit of | d n | < 1.6 × 10 e ⋅cm . This experiment and especially the experiment starting in 1984 at the Institut Laue-Langevin (ILL) pushed the limit down by another two orders of magnitude yielding the best upper limit in 2006, revised in 2015.