Jan Ptaszycki (1854-1912)
Jan Ptaszycki was a Polish mathematician working in St. Petersburg in the period 1876–1912. In Poland, he is forgotten, and in Russia considered generally for Russian mathematician, known there as Ivan Lvovich Ptaszycki. There is no article about it on Polish , while there are three articles in Russian. In historical-mathematical Russian literature, depending on the author, it is reported that Ptaszycki was a Russian mathematician or, more rarely, a Polish mathematician as, for example, in [Lo15a]...