This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Ballon dirigeable en fer portant hommes.tif Ballon dirigeable en fer portant hommes bookmine org tif Konstantin Tsiolkovsky PDold Konstantin Tsiolkovsky
Page 2023 Free-images.com. All images are Public Domain