Original: She further elaborated on them in her magazines The Objectivist Newsletter, The Objectivist, and The Ayn Rand Letter, and in non-fiction books such as Introduction to Objectivist Epistemology and The Virtue of Selfishness.
Simplified: She talked about them more in The Objectivist Newsletter, The Objectivist, The Ayn Rand Letter, Introduction to Objectivist Epistemology and The Virtue of Selfishness.