How do I find the antenna gain (dBi) of a Lenovo X61t laptop?

Does anyone know where I can find the dBi specification for the Lenovo
X61t laptop built-in antenna?

I'm sure it's around 1 to 3 dBi (probably 2dBi - but I'm just guessing).

I want to run realistic calculations of what signal strengths I can pick
up theoretically.

I found all the calculations that I'll run I need in these two files:
http://wndw.net/pdf/wndw2-en/wndw2-ebook.pdf
http://www.cs.uml.edu/~xinwenfu/paper/ICDCS09_Marauder_Fu.pdf

And, I found all the Lenovo X61t internal WiFi card (Intel 4965AGN)
specifications needed in this HP document:
http://tinyurl.com/76pz46a

The one thing I just can't find (which should be easy to find!) is simply
the directional & power specification (dBi) of the built-in Lenovo X61t
laptop antenna!
.