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 vapor pressure <WSD>thermometer</WSD> whose tubing is jacketed through most of the liquid helium . 
Meaning of the word marked with <WSD> tags:  measuring instrument for measuring temperature