Im, Eric Iksoon; Cauley, Jon; Sandler, Todd - In: Kyklos 40 (1987) 2, pp. 238-55
This paper uses spectral analysis to provide evidence that cycles have characterized the following time series: all ter rorist events, skyjackings, kidnappings, barricade and hostage taking and all events not involving hostages. The series for all events ha d a periodicity of 28 months, while...