Official websites use .gov A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Periodical. Levisohn, Reuben, and Sol Spiegelman. "The Cloning of a Self-Replicating RNA Molecule." Proceedings of the National Academy of Sciences of the United States of America 60, 3 (July 1968): 866-872. Article. 7 Images.. Proceedings of the National Academy of Sciences of the United States of America