Krishnamoorthy Sivakumar Yoganand Balagurunathan Edward R. Dougherty Asymptotic joint normality of the granulometric moments. 1537-1543 2001 22 Pattern Recognition Letters 14 http://dx.doi.org/10.1016/S0167-8655(01)00101-5 db/journals/prl/prl22.html#SivakumarBD01