group met "because of a common interest in ideas". Greenspan recalled being drawn to Rand because of a shared belief in "the importance of mathematics and intellectual rigor". The group met at Rand's apartment at least once a week, and would often discuss and debate into the early morning hours. About these discussions, Greenspan said, "Talking to Ayn Rand was like starting a game of chess thinking I was good, and suddenly finding myself in checkmate." Eventually, Rand also allowed them to begin reading the manuscript of Atlas Shrugged (1957) as she completed it. The Collective began to play a larger, more formal role, promoting Rand's philosophy through the Nathaniel Branden Institute (NBI). Some Collective members gave lectures at the NBI in cities across the United States and wrote articles for its newsletters, The Objectivist Newsletter (1962–1965) and The Objectivist (1966–1971). Nathaniel Branden Institute The first formal presentation of Objectivism began with the Nathaniel Branden Lectures (NBL), shortly after the publication of Rand's final novel, Atlas Shrugged. Nathaniel Branden was the first member of The Collective, and later, Rand's "intellectual heir". In time, Branden and Rand became romantically involved. After the publication of Atlas Shrugged, Rand was inundated with requests for more information about her philosophy. Not wanting to be a teacher or leader of an organized movement, she allowed Branden to lecture on her behalf. The success of NBL prompted Branden to expand his lecture organization into the Nathaniel Branden Institute (NBI). Rand and Branden also co-founded the first publication devoted to the study and application of Objectivism. The Objectivist Newsletter began publication in 1962 and was later expanded into The Objectivist. The 1960s saw a rapid expansion of the Objectivist movement. Rand was a frequent lecturer at universities across the country. Rand hosted a radio program on Objectivism on the Columbia University station, WKCR-FM. The Nathaniel Branden Institute (NBI) hosted lectures on Objectivism, the history of philosophy, art, and psychology in cities across the country. Campus clubs devoted to studying Rand's philosophy formed throughout the country, though operated independently of NBI. Rand was a frequent guest on radio and television, as well as an annual lecturer at the Ford Hall Forum. At the peak of its popularity, NBI was delivering taped lectures in over 80 cities. By 1967 NBI had leased an entire floor in the Empire State Building (with The Objectivist as a sub-tenant). In 1968, Rand