1. https://www.statista.com/statistics/398951/global-shipment-figures-for-hard-disk-drives/.
2. https://www.grandviewresearch.com/industry-analysis/permanent-magnets-industry.
3. https://www.statista.com/statistics/266973/global-semiconductor-sales-since-1988/.
4. J. E. Lilienfeld, US Patent 1,745,175 (1926).
5. https://ethw.org/Milestones:Invention_of_the_First_Transistor_at_Bell_Telephone_Laboratories_Inc._1947.