This image was personally created by myself. Kelvin Case publicly licenses all personally created portions of this image under the Creative Commons license. Some portions of this image are derived of images produced by U.S. government sources, specifically from the following image files: File:Atlas EELV family.png, File:Boeing X-37B inside payload fairing before launch.jpg, File:Centaur upper stage of Atlas V rocket.jpg, File:Roundel of the USAF.svg, File:Size Comparison.png, File:X-15.jpg, File:X-15 three view diagram .png, SpaceShipOne image posted at NASA http://www.nasa.gov/multimedia/nasatv/SpaceShipOne.html. Additionally, other image sources were reviewed during the creation of this image. Reference images reviewed in addition to those images listed above are as follows:

• North American X-15 images: In addition to the U.S. government sources listed above, the X-15 images are additionally derived from File:X-15 bewerkt.jpg.
• Space Shuttle image is a derivative work of NASA, specifically from the image listed above.
• Buran image: This Buran image incorporates Wikipedia National flag image File:Flag of the Soviet Union.svg. In addition to the derivative U.S. government sources listed above, this image was entirely and personally created by myself. While drawing the image, I reviewed additional reference images to guide the process, specifically those Buran images posted at http://www.buran.ru/htm/rocket.htm. No copying was done: Those elements of this Buran image that are in addition to the incorporated U.S. government sources (listed above) and national flag image are entirely my own, sole, personal artistic work.
• SpaceShipOne image: The SpaceShipOne images are a derivative work of those U.S. government sources listed above, specifically the NASA image posted at http://www.nasa.gov/multimedia/nasatv/SpaceShipOne.html. In addition, while drawing the image, I reviewed additional reference images to guide the process, specifically those SpaceShipOne images posted at http://richard-seaman.com/Aircraft/AirShows/SpaceShipOne2004/. Wikipedia's SpaceShipOne and Smithsonian Institution National Air and Space Museum's SpaceShipOne images posted at http://nasm.si.edu/exhibitions/gal100/ss1.htm also were reviewed. No copying was done: Those elements of this SpaceShipOne image that are in addition to the incorporated U.S. government sources (listed above) are entirely my own, sole, personal artistic work.
• Boeing X-37 image is a derivative work of those Wikipedia US government images listed above. This image was entirely and personally created by myself. While drawing the image, I reviewed additional reference images to guide the process, specifically those X-37 images posted at http://www.space.com/13230-secretive-37b-space-plane-future-astronauts.html. Wikipedia's Boeing X-37, Atlas V and Centaur also were reviewed. No copying was done: Those elements of this X-37 image that are in addition to the incorporated U.S. government sources (listed above) are entirely my own, sole, personal artistic work.