Since the commercial publication of "The Prospect of Immortality", all those active in cryonics today can trace their involvement, directly or indirectly, to the publication of one or both of Ettinger's books. While Ettinger was the first, most articulate, and most scientifically credible person to argue the idea of cryonics, he was not the only one. In 1962, Evan Cooper had authored a manuscript entitled Immortality: Scientifically, Physically, Now under the pseudonym Nathan Duhring. Cooper's book contained the same argument as did Ettinger's, but it lacked both scientific and technical rigor and was not of publication quality.