An official website of the United States government
The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before
sharing sensitive information, make sure you’re on a federal
government site.
The site is secure.
The https:// ensures that you are connecting to the
official website and that any information you provide is encrypted
and transmitted securely.
Pfefferkorn ER, Pfefferkorn LC.Pfefferkorn ER, et al. Among authors: pfefferkorn lc.J Protozool. 1977 Aug;24(3):449-53. doi: 10.1111/j.1550-7408.1977.tb04774.x.J Protozool. 1977.PMID: 21288