Nikhilananda, Swami - The Gospel of Sri Ramakrishna, 1942

Omananda Puri, Swami - The Boy And The Brothers, 1959

Omananda Puri, Swami - Towards the Mysteries, 1968

Osborne (ed.), Arthur - The Collected Works of Ramana Maharshi, 1959

Osborne (ed.), Arthur - Ramana Maharshi and the Path of Self-Knowledge, 1954

Osborne, Arthur - The Incredible Sai Baba, 1957

Overton Fuller, Jean - Blavatsky and Her Teachers, 1988