Beekmann, W.W.BeekmannSHU-CHENG CHANG2019-10-282019-10-2819860003-889Xhttps://scholars.lib.ntu.edu.tw/handle/123456789/428544A Non-Mu-Unique Multiplicative Trianglejournal article10.1007/BF01195023WOS:A1986D904600010