On-line resources for the following authors are listed below:
A. J. Ayer
Alfred Jules Ayer, Stanford Encyclopedia of Philosophy, plato.stanford.edu.
Gottlob Frege
Gottlob Frege, Stanford Encyclopedia of Philosophy, plato.stanford.edu.
Frege’s Theorem and Foundations for Arithmetic, Stanford Encyclopedia of Philosophy, plato.stanford.edu.
Alexius Meinong
Alexius Meinong, Stanford Encyclopedia of Philosophy, plato.stanford.edu.
George Edward Moore
George Edward Moore, Stanford Encyclopedia of Philosophy, plato.stanford.edu.
George Edward Moore (1873–1958), philosophypages.com.
Gilbert Ryle
Gilbert Ryle, Stanford Encyclopedia of Philosophy, plato.stanford.edu.
Bertrand Russell
Bertrand Russell, Stanford Encyclopedia of Philosophy, plato.stanford.edu.
Writings by Russell: A list of electronic texts of Russell’s books and essays, users.drew.edu.
Ludwig Wittgenstein
Ludwig Wittgenstein, Stanford Encyclopedia of Philosophy, plato.stanford.edu.
Papers of Ludwig Wittgenstein (1889–1951), philosopher, janus.lib.cam.ac.uk.
Wittgenstein Links, helsinki.fi.