1. W. Gugenrath, K. Painter, and D. Whitehouse, “The Portland Vasen,” Glass Studies, 32 (1990), pp. 24–62.
2. M. Bimson and I.C. Freestone, “An Analytical Study of the Portland Vase and Other Roman Cameo Glasses,” J. Glass Studies, 25 (1983), pp. 55–64.
3. D.F. Grose, The Toledo Museum of Art. Early Ancient Glass (New York: Hudson Hills Press, 1989), pp. 259–260 and Fig. 152.
4. Unpublished electron microprobe analyses by the author.
5. Unpublished electron microprobe analyses by the author.