Erik Lindberg Arünas Tamasevicius Gytis Mykolaitis Skaidra Bumeliene Towards Threshold Frequency in Chaotic Colpitts oscillator. 3449-3453 2007 17 I. J. Bifurcation and Chaos 10 http://dx.doi.org/10.1142/S0218127407019196 db/journals/ijbc/ijbc17.html#LindbergTMB07