Paper clip (English Wikipedia)

Petroski, Henry (October 1998). "Polishing the Gem: A First-Year Design Project". Journal of Engineering Education. 87 (4): 445–449. doi:10.1002/j.2168-9830.1998.tb00377.x. S2CID 111237529. Appendix: A selected list of U.S. Patents for paper clips. Journal of Engineering Education, 1998, p. 449.
Trompf, G. W. (October 1969). "Radical Conservatism in Herbert Spencer's Educational Thought". British Journal of Educational Studies. 17 (3): 277. doi:10.2307/3119625. JSTOR 3119625.

earlyofficemuseum.com

History of the Paper Clip. Ad from Cushman & Denison, in The American Lawyer, Sept 1893, p. 3.

O'Connell, James F. (1 July 1995). "Christopher Raven: A Personal Appreciation". Journal of California and Great Basin Anthropology. 17 (1): 10. ISSN 0191-3557. Retrieved 30 September 2021. he often assured beginning graduate students that Herbert Spencer's greatest contribution to humanity had been the invention of the paper clip

"Gem Paper Clip Advertisement by Cushman & Denison". The Phonographic World. 8 (5): XIII. January 1893. hdl:2027/mdp.39015011409193. Retrieved 11 February 2019.

"Cushman & Denison advertisement". The American Lawyer. 1 (9): 3. September 1893. Retrieved 9 February 2019.

"Paper Clip". The Great Idea Finder. Archived from the original on 2016-11-14. Retrieved 2010-07-20.

Trompf, G. W. (October 1969). "Radical Conservatism in Herbert Spencer's Educational Thought". British Journal of Educational Studies. 17 (3): 277. doi:10.2307/3119625. JSTOR 3119625.

"Useful Registered Design Number: 809". BT 45 — Patents, Designs and Trade Marks Office: Non-ornamental ('Useful') Designs Act 1843 Representations. London: National Archives. 2 September 1846. Retrieved 30 September 2021.

Grace, Valerie (December 28, 2003). "Get a grip: Popularity of paper clips continue through the years". The Times Recorder (Zanesville, Ohio, U.S.). p. D1.

Son of Rudolph Ackermann; see Spencer (1904) p.354 "Mr. Ackermann who was a bad man of business, and who, failing not long afterwards, shot himself"; and "Rudolph Ackermann". British artists' suppliers, 1650-1950. National Portrait Gallery. Retrieved 29 September 2021. Adolphus Ackermann also set up business close by at 15 Beaufort Buildings but committed suicide in 1858 when faced with bankruptcy proceedings

Brown, Peter (September 1, 2009). "The Paper Clip". Scientific American. Retrieved December 12, 2018.

Petroski, Henry (October 1998). "Polishing the Gem: A First-Year Design Project". Journal of Engineering Education. 87 (4): 445–449. doi:10.1002/j.2168-9830.1998.tb00377.x. S2CID 111237529. Appendix: A selected list of U.S. Patents for paper clips. Journal of Engineering Education, 1998, p. 449.

"Paper Clip". The Great Idea Finder. Archived from the original on 2016-11-14. Retrieved 2010-07-20.

O'Connell, James F. (1 July 1995). "Christopher Raven: A Personal Appreciation". Journal of California and Great Basin Anthropology. 17 (1): 10. ISSN 0191-3557. Retrieved 30 September 2021. he often assured beginning graduate students that Herbert Spencer's greatest contribution to humanity had been the invention of the paper clip

Osdol, Paul Van (1 September 2015). "Pittsburgh dentist admits using paper clips for root canals". Retrieved 22 January 2018.