Fisher's Information Matrix

Hi guys,

I am trying to implement an Active Learning algorithm using the Fisher's Information Matrix as the selection strategy. I tried different papers but I couldn't understand how the matrix is obtained. Some of these papers are:

A Probability Analysis on the Value of Unlabeled Data for Classification Problems Tong Zhang, Frank J. Oles

Active Learning for Logistic Regression: an evaluation Andrew I. Schein, Lyle H. Ungar

I will be grateful if someone can explain this matrix or provide me with good references. A reference implementation would be really nice too.

Thanks!