250 / | HD | RADIANT ENERGY |
253 | DF | GEOLOGICAL TESTING OR IRRADIATION {3} |
256 | DF | .~ Well testing apparatus and methods {9} |
269.1 | DF | .~.~ With source and detector {4} |
269.4 | DF | .~.~.~ Having neutron source and neutron detector {1} |
269.5 | .~.~.~.~ Having thermal neutron detector |