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Fig. 2 Our fi rst two collaborative papers. On left is Popper and Fay ( 1973 ) and on the right Fay
and Popper ( 1974 )
A.N. Popper and R.R. Fay
Fig. 2 Our fi rst two collaborative papers. On left is Popper and Fay ( 1973 ) and on the right Fay
and Popper ( 1974 )
A.N. Popper and R.R. Fay