DescriptionCharlesKoch'sSignature.png English: CharlesKoch'sSignature Date 1 January 2021 Source https://news.kochind.com/news/2020/how-koch-is-fighting-covid-19
DescriptionPortrait of Nathan Cooley Keep.png English: Portrait of Nathan Cooley Keep with the signature. From Koch, Charles R. E. (1909). History of dental surgery