Kongsheng Zhang Jinguan Lin Chao Huang 0005 Some New Results on Weighted Geometric mean for copulas. 277-288 2013 21 Int. J. Uncertain. Fuzziness Knowl. Based Syst. 2 https://doi.org/10.1142/S0218488513500153 db/journals/ijufks/ijufks21.html#ZhangLH13