Subject: Habitable zones, how are they calculated (formulas, not conjecture)?

I looking through this webpage on extrasolar planets
http://www.extrasolar.net/planettour.asp?StarCatId=normal&PlanetId=158
I notices very detail habitable zone diagrams. I understand that there are 
very specific figures that can be determined (and would be needed for these 
diagrams) and I would like to know the formula, Not the conjecture on the 
definition of a "Habitable Zone," but how these specific range figures are 
calculated.

http://en.wikipedia.org/wiki/Habitable_zone
^This site gives a formula for a median, but the chart shows a band/range.

http://www.solstation.com/habitable.htm
^This website gives the ranges for our solar system:
"the HZ for our own Solar System currently extends from at least 0.95 AU to 
1.37 AU"

I searched the archives, nothing comes up on HZ ranges, so please consider my 
question again.
Thanks,
Gabriel

PS: you may need an Astrophysics category. And I notice that Angelle Tanner 
(UCLA) likes answering these questions.

Re: Habitable zones, how are they calculated (formulas, not conjecture)?