“…Nuclear measurement techniques were first used in 1939 (3) and, since that time, have come to play a dominant role in the analysis of subsurface ELUS, SCHWEITZER & ULLO geology. The developments in nuclear techniques have been motivated by a desire to generate a better understanding of the subsurface geology for the location and evaluation of oil, gas, and mineral resources (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21), as welI as for a better understanding of geological processes (22).…”