Q12a: How can you make a chaotic oscillator?  
A12a: Two references are:  
  
1. T. S. Parker and L. O. Chua, Chaos: a tutorial for engineers,  
_Proceedings IEEE_ 75 (1987), pp. 982-1008.  
  
2. _New Scientist_, June 30, 1990, p. 37.  
  
Q12b: What are laboratory demonstrations of chaos?  
A12b: Robert Shaw at UC Santa Cruz experimented with chaos in dripping  
taps. This is described in:  
  
1. J. P. Crutchfield, Chaos, _Scientific American_ 255, 6 (Dec. 1986), pp.  
38-49.  
  
2. I. Stewart, _Does God Play Dice?: the Mathematics of Chaos_,  
B. Blackwell, New York, 1989.  
  
Two references to other laboratory demonstrations are:  
  
1. K. Briggs, Simple Experiments in Chaotic Dynamics, _American Journal  
of Physics_ 55, 12 (Dec 1987), pp. 1083-1089.  
  
2. J. L. Snider, Simple Demonstration of Coupled Oscillations, _American  
Journal of Physics_ 56, 3 (Mar 1988), p. 200.