Alberto Calderon's famous paper that layed the foundations for the mathematical study of the inverse conductivity boundary value problem (inverse problem for electrical impedance tomography) appeared only in the form of a crudely typed conference proceedings. Copies circulate with scribbled notes and annotations but originals are rarely seen. My copy for example has annotations by Bob Kohn.
For the benefit of those starting out in the subject who do not have a copy, I have scanned mine as a pdf file. It is a bit faint and you can't see the annotations by Kohn (which are useful).
To see the paper click on the full reference below.
A.P. Calderón, ON AN INVERSE BOUNDARY VALUE PROBLEM, in Seminar on Numerical Analysis and its Applications to Continuum Physics, Rio de Janeiro, Editors W.H. Meyer and M.A. Raupp, Sociedade Brasileira de Matematica, (1980). 65-73.
The full proceedings were reviewed in Mathematical Reviews MR0590268 (81i:65003) which confirms the page number (sometimes mis quoted as 1-7), Note also that a paper was given by Eli and David Isaacson at that meeting, Calderon's paper is reviewed in Maths Rev by JR Cannon MR0590275 (81k:35160) . The links might not work if you do not have a subscription to MathSciNet.
UPDATE. The paper has been reprinted in "Computational and Applied Mathematics"
in 2006. The reference is:
CALDERON, Alberto P. On an inverse boundary value problem. Mat. apl. comput., 2006, vol.25, no.2-3, p.133-138. ISSN 0101-8205. Availiable online
Here is a link to
Sociedade Brasileira de Matematica (Brazilian Mathematics Society).
Here are a few related references, see also list of papers citing Calderon 1980
Some papers that cite Calderon's paper can by found on Citeseer
This page is linked to by the Wikipedia article Electrical Impedance Tomography and in Electrical Resistivity TomographyPage maintained by Bill Lionheart