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. Mertz, Janet E., and Paul Berg. "Viable Deletion Mutants of Simian Virus 40: Selective Isolation by Means of a Restriction Endonuclease from Hemophilus parainfluenzae." Proceedings of the National Academy of Sciences of the United States of America 71, 12 (December 1974): 4879-4883. Article. 5 Images.. Proceedings of the National Academy of Sciences of the United States of America