- National Coal Council (U.S.)1
- National Governors' Association2
- National Lumber and Building Material Dealers Association (U.S.)1
- National Petroleum Council1
- Navajo Tribe of Arizona, New Mexico & Utah3
- Nixon, Richard M. (Richard Milhous), 1913-19943
- O'Neill, Tip1
- Oil, Chemical, and Atomic Workers International Union1
- Organization of Petroleum Exporting Countries1
- Osage Tribe, Oklahoma1
- Ottawa Tribe2
- Pawnee Indian Tribe of Oklahoma2
- Pepper, Claude, 1900-19891
- Poage, W. R. (William Robert), 1899-19871
- Ponca Tribe of Indians of Oklahoma1
- Preyer, Richardson1
- Pritchard, Joel M. (Joel McFee), 1925-19971
- Public Citizen, inc. Congress Watch1
- Rahall, Nick J., 1949-3
- Randolph, Jennings, 1902-19982
