A version of the 1998 volume Ceramica in Italia. 6-7 secolo. Atti del convegno in onore di John W. Hayes : Roma, 11-13 maggio 1995 has long been available on the internet as a series of PDFs. I say a version because the pages in each file are unnumbered and some spelling errors were introduced into the text by the digital conversion process.
The location of these files has changed over time and they are now on the Portale di Archeologia Medievale of the Dipartimento di Archeologia e Storia delle Arti of the Università di Siena.
Despite its editorial shortcomings, it's worth having access to the digital version of this publication. But there is no direct link on the Siena website. Instead, you can use the following two curl commands to download the individual files:
curl -o vol1_#1.pdf http://archeologiamedievale.unisi.it/NewPages/COLLANE/TESTIBAM/ceramica/[01-29].pdf
curl -o vol2_#1.pdf http://archeologiamedievale.unisi.it/NewPages/COLLANE/TESTIBAM/ceramica/vol2/[01-26].pdf
[I'm sure some browsers will wrap these long lines or have other problems so make sure everything from 'curl' to 'pdf' is on one line when you paste each command into your shell.]
You'll end up with 55 PDFs in whichever directory you started the download.
The curl program should already be on your machine if you're running Mac OS X or another Unix-like OS. If not, it should be trivial to install it. A windows version is available from the curl download page.