Complex sentence: He was an associate of Ayn Rand, working with her on "The Ayn Rand Lexicon" and helping her edit the second edition of Rand's "Introduction to Objectivist Epistemology".
Split into simpler sentences: He was an associate of Ayn Rand, working with her on "The Ayn Rand Lexicon". He helped edit the second edition of Rand's "Introduction to Objectivist Epistemology".