References - orthorectification & stereo extraction of DEMs

I would like to learn more about orthorectification of imagery
and extraction of digital elevation models from stereo imagery.
Can anyone recommend good references for both of these topics?

Thanks,
Ken Hardis
Visual Systems Scientist
Insitute for Simulation & Training/
   Visual Systems Lab
University of Central Florida

E-mail - hardis@vsl.ist.ucf.edu
Phone - 407/658-5511

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Ken Hardis Institute for Simulation & Training
                     Visual Systems Lab
                     hardis@vsl.ist.ucf.edu , (407) 658-5511
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