Oops, my post deleted when I went to fix the formatting!
There are two papers you may be referring to, for both of which you may need
library assistance; I haven't seen them online. I have the QT volume, but it's in offsite storage.
A.
Burnett, 'The Romano-campanian silver', in La monetazione Romano-
Campana, Atti del X Convegno, Napoli 1993, Roma, 19-47
A
Burnett, The First
Roman Silver Coins, Andrew
Burnett, Quaderni Ticinesis, Lugano 1978
However, there are sometimes cross-references in high-end
auctions and other online sources, so you may be able to find what you are looking for indirectly.