Wikipedia, the open online encyclopedia that's written and monitored by volunteers, has changed its rules for submitting articles after a posting incorrectly linked the assassination of Robert F. Kennedy to a former administrative assistant.

A May 26 posting on John Seigenthaler Sr., an assistant to the attorney general in the early 1960s, said Seigenthaler was "thought to have been directly involved in the Kennedy assassinations of both (President) John (F. Kennedy), and his brother, Bobby."

Although Wikipedia founder Jimmy Wales has said that erroneous submissions are usually corrected within minutes, the Seigenthaler "biography" stayed on the site for 132 days before it was corrected. In addition, the "scurrilous text" appeared on search engines Reference.com and Answers.com, Seigenthaler said in a Nov. 29 editorial in USA Today.

"I have no idea whose sick mind conceived the false, malicious 'biography' that appeared under my name for 132 days on Wikipedia, the popular, online, free encyclopedia whose authors are unknown and virtually untraceable," Seigenthaler said.

In acknowledging the incident, Wales said Monday it was an unusual case in which the site's safeguards failed.

"It slipped through the cracks is basically what happened," Wales said.

New articles submitted to the site are first looked over by volunteer editors, who categorize and post the submissions. In this case, only minor changes and a couple of links were added.

"Somehow in the process, this article got overlooked," Wales said.

As a result of the incident, Wikipedia no longer accepts new submissions from anonymous contributors, Wales said. A person now has to register with the site before contributing an article. By doing this, site managers can at least determine whether a person associated with a specific user ID is submitting false information, and prevent articles from being submitted by that registrant.