APA (7th ed.) Citation

Phelps, G. (1929). Trade opportunity for automatic weighing machinery. [publisher not identified].

Chicago Style (17th ed.) Citation

Phelps, Gordon. Trade Opportunity for Automatic Weighing Machinery. Washington, D.C.: [publisher not identified], 1929.

MLA (9th ed.) Citation

Phelps, Gordon. Trade Opportunity for Automatic Weighing Machinery. [publisher not identified], 1929.