Assertion: zone refining | /r/HasProperty | developed by william gardner pfann
Facets:
value: in bell labs
type: LOCATION
value: further
type: DEGREE
value: as a method
type: MANNER
Source sentences:
text: Zone refining was invented by John Desmond Bernal and further developed by William Gardner Pfann in Bell Labs as a method to prepare high purity materials, mainly semiconductors, for manufacturing transistors.