English: Figure 6-12. Comparison of postflight percent change in knee extensor and flexor strength from preflight in Shuttle (STS), the three Skylab missions (SL2-4), NASA-Mir (Mir), and ISS.
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]