Höhler, P. & v. Köppen, I. Experimental Flights for Testing of a Reactor as an Expedient for the Termination of Dangerous Spins, report, July 1949; (https://digital.library.unt.edu/ark:/67531/metadc64981/m1/1/: accessed January 19, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .