Woodward, Angela. «How Products Are Made. Volume 7. Pape Clip»(en inglés). Consultado el 20 de agosto de 2012. «The second method was to take a common straight pin and pin the sheets together.»
Woodward, Angela. «How Products Are Made. Volume 7. Paper Clip»(en inglés). Consultado el 20 de agosto de 2012. «The finished appearance of the clip is also a design consideration. The clip can have various finishes, smooth or slightly serrated, shiny or dull, and it can be made in many different sizes.»
Woodward, Angela. «How Products Are Made. Volume 7. Paper Clip»(en inglés). Consultado el 20 de agosto de 2012. «The earliest recorded patent for a paper clip was granted by the United States Patent Office to a Pennsylvanian, Matthew Schooley, in 1898.»
