Reimus, M.A.H. & Rinehart, G.H. Light-Weight Radioisotope Heater Unit (LWRHU) sequential impact tests, report, August 1, 1997; (https://digital.library.unt.edu/ark:/67531/metadc690571/m1/1/: accessed December 13, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .