by  The Wittgenstein Archives at the University of Bergen

• The Royal Institute of Philosophy
• The Internet Encyclopedia of Philosophy
• Stanford Encyclopedia of Philosophy
• Dictionary of Philosophy of Mind
• Dictionary of Philosophical Terms and Names
• Österreich Lexikon
• Philosophenlexikon
• Kirchenlexikon
• Beats Biblionetz
• Philosophy Research Base
• The Knitting Circle: Philosophy
• Architekturzentrum Wien: Haus Wittgenstein
• Enciclopedia Multimediale delle Scienze Filosofiche: Ludwig Wittgenstein
• EMSF: Wittgenstein
• SWIF: Ludwig Wittgenstein
• Moritz-Schlick-Projekt
• Institut Nicod