Figure 6-7. LET dependence of RBE of radiation in producing emesis or retching in a ferret. B = bremstrahlung; e– = electrons; P = protons; 60Co = cobalt gamma rays; n0 = neutrons; and 56Fe = iron.
The NASA website hosts a large number of images from the Soviet/Russian space agency, and other non-American space agencies. These are not necessarily in the public domain.
The SOHO (ESA & NASA) joint project implies that all materials created by its probe are copyrighted and require permission for commercial non-educational use. [2]