From the Articles of Impeachment adopted by House Judiciary Committee on July 27, 1974:
Richard M. Nixon, using the powers of his high office, engaged personally and through his close subordinates and agents, in a course of conduct or plan designed to delay, impede, and obstruct the investigation of such illegal entry; to cover up, conceal and protect those responsible; and to conceal the existence and scope of other unlawful covert activities.
The means used to implement this course of conduct or plan included one or more of the following… interfering or endeavouring to interfere with the conduct of investigations by the Department of Justice of the United States, the Federal Bureau of Investigation, the office of Watergate Special Prosecution Force, and Congressional Committees.”