French mathematician, physicist, and philosopher of science (1854–1912) who famously formulated the ‘Poincare Conjecture,’ which went unsolved for nearly a century. Scarce ALS in French, signed “Poincare,” one page, 4.5 x 7, no date. Untranslated letter to social psychologist Gustave Le Bon, regretfully declining an invitation to attend a banquet due to sickness. In fine condition. Pre-certified PSA/DNA.
This item is Pre-Certified by PSA/DNA
Buy a third-party letter of authenticity for
$150.00
*This item has been pre-certified by a trusted third-party authentication service, and by placing a bid on this item, you agree to accept the opinion of this authentication service. If you wish to have an opinion rendered by a different authenticator of your choosing, you must do so prior to your placing of any bid. RR Auction is not responsible for differing opinions submitted 30 days after the date of the sale.
