Manual of classification of subjects of invention of the United States Patent office.
Rev. to January 1, 1912 (including classification bulletin no. 27)

APA Citation

United States. Patent Office. (1912). Manual of classification of subjects of invention of the United States Patent office: Rev. to January 1, 1912 (including classification bulletin no. 27). Washington: Govt. print. off..

MLA Citation

United States. Patent Office. Manual of Classification of Subjects of Invention of the United States Patent Office: Rev. to January 1, 1912 (including Classification Bulletin No. 27). Washington: Govt. print. off., 1912.