Sentence:  Several germanium resistors have been thermally cycled from 300 to 4.2 * * f and their resistances have been found to be reproducible within 1 3 millidegree when temperatures were derived from a <WSD>vapor</WSD> pressure thermometer whose tubing is jacketed through most of the liquid helium . 
Meaning of the word marked with <WSD> tags:  the pressure exerted by a vapor; often understood to mean saturated vapor pressure (the vapor pressure of a vapor in contact with its liquid form)