NASA Armstrong Fact Sheet: Helios Prototype Helios Prototype fact sheet – old edition; archived at archive.org Investigation of the Helios Prototype Aircraft Mishap – Volume 1, T.E. Noll et al., January 2004 "Aviation and Space World Records".
NASA Helios factsheet NASA Helios fact sheet — old edition; archived at archive.org Investigation of the Helios Prototype Aircraft Mishap — Volume 1, T.E. Noll et al., January 2004 Aviation and Space World Records (неопр.).