In 1898, at the age 21, he was the author of ten mathematical papers and received his doctor's degree at Uppsala University for the thesis On system of linear total differential equations particularly with 2n-periodic coefficients.
Sa 1898, sa edad na 21, siya ang may-akda ng sampung matematiko papeles at natanggap ng kanyang doktor's degree sa Uppsala University para sa tisis Sa sistema ng kabuuang haba kaugalian lalo na equation na may panaka-2n-coefficients.