The 1931 international code of signals.
Vol. II,
For radio signaling ...

APA Citation

Great Britain. Board of Trade. (1933). The 1931 international code of signals. American ed. Washington: U. S. Govt. print. off..

MLA Citation

Great Britain. Board of Trade. The 1931 International Code of Signals. American ed. Washington: U. S. Govt. print. off., 1933.

Warning: These citations may not always be complete (especially for serials).