Zamenhof Day (but not the international English one), bore a special version of their logo (a Doodle) emblazoned with the Esperanto flag in honor of the occasion, which generated, on the 30 biggest Wikipedia languages, 1,750,000 page views on the articles "L. L. Zamenhof". Zamenhof Day Zamenhof Day (), also called Esperanto Book Day, is celebrated on 15 December, the birthday of Esperanto creator L. L. Zamenhof. It is the most widely celebrated day in Esperanto culture. On this day, Esperantists hold information sessions and cultural gatherings to promote literature in Esperanto. The history of celebrating Esperanto on Zamenhof's birthday can be
Ludwik Birkenmajer w przekładzie polskim" (1920) · Mikołaj Kopernik, "O obrotach ciał niebieskich i inne pisma" (2004) · Andrzej Śródka, "Uczeni polscy XIX-XX stulecia". Warszawa 1994, vol. I, p. 155-157 . Paweł Tarasiewicz, Zbigniew Pańpuch, "Birkenmajer Ludwik Antoni", "Powszechna encyklopedia filozofii" vol. I, Lublin 2000 · Władysław Horbacki, "Ludwik Antoni Birkenmajer (1855-1929)". Łódź 1930 Ludwik Birkenmajer Ludwik Antoni Birkenmajer (18 May 1855 - 20 November 1929), Polish historian of science, physicist, astronomer, professor of the Jagiellonian University. Descended from the German family settled in Galicia (Southern Poland) during the time of the Napoleon wars, later a part of the Austrian Habsburg Empire.