; Yu. A. Koševnik, B. Ya. Levit, “On a non-parametric analogue of the information matrix”, Theory Probab. Appl., 21:4 (1976), 
; Yu. A. Koševnik, B. Ya. Levit, “On a non-parametric analogue of the information matrix”, Theory Probab. Appl., 21:4 (1976),