December 27, 1971 - January 2, 1972
You might find this article interesting, it is not behind a paywall. https://www.nytimes.com/1971/01/15/archives/mystery-in-illinois-millionaire-aide-mystery-in-illinois-how-30000.html
You might find this article interesting, it is not behind a paywall. https://www.nytimes.com/1971/01/15/archives/mystery-in-illinois-millionaire-aide-mystery-in-illinois-how-30000.html