Chaotic Circuits and Encryption by Brad Aimone & Stephen Larson:
http://matdev-calit2.ucsd.edu/neurophysics/courses/physics_173_273/AimoneLarsonChaos.pdf
Chua's Circuit by Michael Cross:
http://crossgroup.caltech.edu/chaos_new/Chua.html
Simple Chaotic Systems and Circuits by J.C. Sprott:
http://sprott.physics.wisc.edu/pubs/paper245.htm
SIMPLEST CHAOTIC CIRCUIT by Bharathwaj muthuswamy & Leon O. Chua:
http://myweb.msoe.edu/muthuswamy/pubs/SimplestChaoticCircuit.pdf