P. Gu et al.YEE HSIUNG2018-09-102018-09-101994http://inspirehep.net/record/378564http://scholars.lib.ntu.edu.tw/handle/123456789/308756Measurement of the branching ratio and a study of CP for the leptonic decay K(L) ---> e+ e- e+ e-journal article10.1103/PhysRevLett.72.3000