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 of scholars. He was married Zofia (Sophie), the daughter of Franciszek Karliński, the professor of astronomy in the Jagiellonian University, and inherited his library embracing mostly the books on mathematics and physics. They had three sons: Aleksander Ludwik (historian of culture and exact sciences, and bibliologist), Józef (poet, interpreter and literature historian), and Wincenty (Polish philologist, teacher and renown Tatra Mountains-climber). His grandson is Krzysztof Birkenmajer (professor of geology, member of the Polish Academy of Sciences). In 2011 the Institute for the History of Science of the Polish Academy of Sciences received the name of father and son: Ludwik &