Section 1920 Citation of Prior Art Under 37 CFR 1.501(a)

37 CFR 1.501(a) permits any person at any time during the period of enforceability of a patent to cite to the Office, in writing, prior art consisting of patent and printed publications which that person states to be pertinent and applicable to the patent and believes to have a bearing on the patentability of any claim(s) of the patent. See MPEP § 2202§ 2208.