United States. Bureau of Mines. (1938). List of respiratory protective devices approved by Bureau of Mines; First supplement to Information circular 7030, new approvals. [s.n.].
Chicago Style (17th ed.) CitationUnited States. Bureau of Mines. List of Respiratory Protective Devices Approved by Bureau of Mines; First Supplement to Information Circular 7030, New Approvals. [Washington]: [s.n.], 1938.
MLA (9th ed.) CitationUnited States. Bureau of Mines. List of Respiratory Protective Devices Approved by Bureau of Mines; First Supplement to Information Circular 7030, New Approvals. [s.n.], 1938.
Warning: These citations may not always be 100% accurate.