What algorithm is behind the functionality "Event" of odesolver?

I sometimes use the "Event" functionality in my odesolver to stop the integration at same conditions. It works well. Do you know the references (eg: paper, textbooks,...) of this algorithm?

Thanks

[Matteo]

Investigating the code, I found the 'Event' functionality is managed by odezero function. Odezero seems to use a 'Regula Falsi' method to find a possible crossing. Nevertheless this function calls ntrp45 (for example). I think this is the real engine to find the Event result. In fact the header reports: "Interpolation helper function for ODE45". Therefore, my question would be how this subroutine works