1. Typical Wallace and Tiernan gauges are models FA 160 and 61A‐ID‐0800, obtainable from Wallace and Tiernan, 25 Main St., Belleville, NJ 07109.
2. MKS Baraton type 77, obtainable from MKS Instruments Inc., 45 Middlesex Turnpike, Burlington, MA.
3. D. Alpert et al., Rev. Sci. Instrum. 22, 370 (1951).RSINAK0034-6748
4. J. M. Luss and J. A. Morrison, Rev. Sci. Instrum. 22, 805 (1951).RSINAK0034-6748
5. J. R. Anderson, Rev. Sci. Instrum. 29, 1073 (1958).RSINAK0034-6748