"Archived copy"(PDF). invention.smithsonian.org. Archived from the original(PDF) on 7 August 2010. Retrieved 12 January 2022.{{cite web}}: CS1 maint: archived copy as title (link)
"Archived copy"(PDF). invention.smithsonian.org. Archived from the original(PDF) on 7 August 2010. Retrieved 12 January 2022.{{cite web}}: CS1 maint: archived copy as title (link)