Krishnamurti continued speaking in public lectures, group discussions and with concerned individuals around the world. In the early 1960s, he made the acquaintance of physicist David Bohm, whose philosophical and scientific concerns regarding the essence of the physical world, and the psychological and sociological state of mankind, found parallels in Krishnamurti's philosophy. The two men soon became close friends and started a common inquiry, in the form of personal dialogues–and occasionally in group discussions with other participants–that continued, periodically, over nearly two decades. Several of these discussions were published in the form of books or as parts of books, and introduced a wider audience (among scientists) to Krishnamurti's ideas. Although Krishnamurti's philosophy delved into fields as diverse as religious studies, education, psychology, physics, and consciousness studies, he was not then, nor since, well known in academic circles. Nevertheless, Krishnamurti met and held discussions with physicists Fritjof Capra and E. C. George Sudarshan, biologist Rupert Sheldrake, psychiatrist David Shainberg, as well as psychotherapists representing various theoretical orientations. The long friendship with Bohm went through a rocky interval in later years, and although they overcame their differences and remained friends until Krishnamurti's death, the relationship did not regain its previous intensity.