Popkess, Athelstan (1 January 1933). "Pursuit by wireless: The value of mobility". The Police Journal: Theory, Practice, and Principles. 6 (1): 31. doi:10.1177/0032258X3300600106. S2CID148826051.
Popkess, Athelstan (1 January 1933). "Pursuit by wireless: The value of mobility". The Police Journal: Theory, Practice, and Principles. 6 (1): 31. doi:10.1177/0032258X3300600106. S2CID148826051.