Researches in stellar photometry during the years 1894 to 1906, made chiefly at the Yerkes observatory Q Science
Bonner zoologische Beiträge : Herausgeber: Zoologisches Forschungsinstitut und Museum Alexander Koenig, Bonn Q Science
Memorie della R. Accademia delle scienze dell’Istituto di Bologna, Classe di scienze fisiche Q Science
