Dear Todd,

> I couldn't find a free copy of  that paper, but this one has a pdf available and seems to cover the basics (and it is by the same group so it has some of the same figures and most of the same equations).  I may use it in the docstring instead.  You really only need to read the first two pages (second and third pages of the pdf since the first page is just citation information).
>
> http://scitation.aip.org/content/aip/journal/chaos/21/4/10.1063/1.3670512
>
> van Hemmen, JL, Longtin, A, and Vollmayr, AN. 
> Testing resonating vector strength: Auditory system, electric fish, and noise.  
> Chaos 21, 047508 (2011); http://dx.doi.org/10.1063/1.3670512

Thanks a lot for this new reference .... I searched too for a free copy of the first one without success.

Cheers,
Eraldo