William Mark Felt Sr. (August 17, 1913 – December 18, 2008) was a Federal Bureau of Investigation (FBI) special agent who served as the Bureau's Associate Director, the FBI's second-highest-ranking post, from May 1972 until his retirement from the FBI in June 1973.
 During his time as Associate Director, Felt served as an anonymous informant, nicknamed "Deep Throat", to reporters Bob Woodward and Carl Bernstein of "The Washington Post", providing them critical information about the Watergate scandal, a scandal which ultimately led to the resignation of President Richard M. Nixon in 1974.
 Though Felt's identity as Deep Throat was strongly suspected by some in Washington, including Nixon himself, and was speculated by many others, it generally remained a secret for the next 30 years.
 In 2005, Felt finally acknowledged that he was Deep Throat, after being persuaded to reveal his identity by his family.
An impeachment process against Richard Nixon was formally initiated on February 6, 1974, when the United States House of Representatives passed a resolution, , giving its Judiciary Committee authority to investigate whether sufficient grounds existed to impeach Richard Nixon, the 37th President of the United States of high crimes and misdemeanors, primarily related to the Watergate scandal.
 This investigation was undertaken one year after the United States Senate established a select committee to investigate the 1972 break-in at the Democratic National Committee headquarters at the Watergate office complex in Washington, D.C. and the Nixon Administration's attempted cover-up of its involvement.
Kenneth Harry Dahlberg (June 30, 1917 – October 4, 2011) was an American businessman and highly decorated World War II fighter ace.
 According to reporter Bob Woodward, a check made out to Dahlberg was a key part in connecting the Watergate scandal to President Richard Nixon's re-election campaign, though Dahlberg himself was not accused of any wrongdoing.
Harry M. Rosenfeld (born August 12, 1929) is an American newspaper editor who was the editor in charge of local news at "The Washington Post" during the Richard Mattingly murder case and the Watergate scandal.
 He oversaw the newspaper's coverage of Watergate and resisted efforts by the paper's national reporters to take over the story.
 Though "Post" editor-in-chief Benjamin C. Bradlee gets most of the credit, managing editor Howard Simons and Rosenfeld worked most closely with reporters Bob Woodward and Carl Bernstein on developing the story.
 Rosenfeld published a memoir including an account of his work at the Post in 2013.
Deep Throat is the pseudonym given to the secret informant who provided information in 1972 to Bob Woodward, who shared it with Carl Bernstein.
 Woodward and Bernstein were reporters for "The Washington Post", and Deep Throat provided key details about the involvement of U.S. President Richard Nixon's administration in what came to be known as the Watergate scandal.
 In 2005, 31 years after Nixon's resignation and 11 years after Nixon's death, a family attorney stated that former Federal Bureau of Investigation Associate Director Mark Felt was Deep Throat.
 Felt was suffering from dementia at the time and had previously denied being Deep Throat, but Woodward and Bernstein confirmed the attorney's claim.
The Watergate scandal was a major political scandal that occurred in the United States in the early 1970s, following a break-in at the Democratic National Committee (DNC) headquarters at the Watergate office complex in Washington, D.C. on June 17, 1972, and President Richard Nixon’s administration’s attempted cover-up of its involvement.
 When the conspiracy was discovered and investigated by the U.S. Congress, the Nixon administration’s resistance to its probes led to a constitutional crisis.
All the President's Men is a 1976 American political thriller film about the Watergate scandal.
 Directed by Alan J. Pakula with a screenplay by William Goldman, it is based on the 1974 non-fiction book of the same name by Carl Bernstein and Bob Woodward, the two journalists investigating the Watergate scandal for "The Washington Post".
 The film stars Robert Redford and Dustin Hoffman as Woodward and Bernstein, respectively; it was produced by Walter Coblenz for Redford's Wildwood Enterprises.
The War Within: A Secret White House History (2006–2008) is a non-fiction book by "Washington Post" reporter Bob Woodward that was released by publisher Simon & Schuster on September 8, 2008.
 It is the fifteenth book written by Woodward, the fourth in a series of books about President George W. Bush and his administration's foreign policy including "Bush at War", "Plan of Attack", and "State of Denial".
 The book discusses the debate within the administration about the controversial Iraq "surge" strategy implemented in 2007.
 Simon & Schuster editor Alice Mayhew said in an official statement that “There has not been such an authoritative and intimate account of presidential decision making since the Nixon tapes and the Pentagon Papers.
 This is the declassification of what went on in secret, behind the scenes.”
The Final Days is a 1976 non-fiction book written by Bob Woodward and Carl Bernstein about the Watergate scandal.
 A follow up to their book "All the President's Men", "The Final Days" concerns itself with the final months of the Presidency of Richard Nixon including battles over the Nixon White House tapes and the impeachment process against Richard Nixon.
All the President's Men is a 1974 non-fiction book by Carl Bernstein and Bob Woodward, two of the journalists investigating the first Watergate break-in and ensuing scandal for "The Washington Post".
 The book chronicles the investigative reporting of Woodward and Bernstein from Woodward's initial report on the Watergate break-in through the resignations of H. R. Haldeman and John Ehrlichman, and the revelation of the Nixon tapes by Alexander Butterfield in 1973.
 It relates the events behind the major stories the duo wrote for the "Post", naming some sources who had previously refused to be identified for their initial articles, notably Hugh Sloan.
 It also gives detailed accounts of Woodward's secret meetings with his source Deep Throat whose identity was kept hidden for over 30 years.
 Gene Roberts, the former executive editor of "The Philadelphia Inquirer" and former managing editor of "The New York Times", has called the work of Woodward and Bernstein "maybe the single greatest reporting effort of all time."

Question: Which 1976 non-fiction book written by Bob Woodward is about the Watergate scandal leading to Nixon's impeachment?
Answer: The Final Days