TSpectrum::Search

In the documentation for TSpectrum::Search we have the following definition for sigma:

What manual is this in reference to? I do not find the explanation in the ROOT manual? Can this be expanded upon in the documentation or the location of “manual” be more clearly indicated?

Anyone out there know what manual this is referring to?

Perhaps it’s the one mentioned in the description in the TSpectrum class:
ftp://root.cern.ch/root/Spectrum.doc