Mary Walton McCandlish Livingston, a federal archivist whose testimony before Congress revealed that President Nixon's donated papers were improperly backdated, died March 23 in Alexandria, Va. She was 92 and had Alzheimer's disease.

Livingston, a senior archivist in the Office of Presidential Libraries at the National Archives for 30 years, supervised work on Nixon's early papers. In March 1970, while working with a manuscript dealer chosen by Nixon, she selected 1,176 boxes of personal papers that the president intended to donate to the nation.

A change in federal tax law would have prevented Nixon from taking a deduction for the donation. But the dealer prepared an affidavit that said Nixon donated his vice presidential papers a year earlier than he actually did, which gave the president a $450,000 tax break.

Public indignation at Nixon's nonpayment of federal taxes led to a hearing before the Joint Committee on Internal Revenue Taxation. Livingston testified that the president could not have donated the papers in 1969 because the dealer asked her to select the papers a year later.

Reporter Mary McGrory's Page One column in the Washington Star-News dubbed Livingston "A Proper Civil Servant."