APA

United States, . (1988). Former Presidents: support costs and other information. [Washington, D.C: .

Chicago

United States, . 1988. Former Presidents: support costs and other information. [Washington, D.C: .

Harvard

United States, . (1988). Former Presidents: support costs and other information. [Washington, D.C: .

MLA

United States, . Former Presidents: support costs and other information. [Washington, D.C: . 1988.