Subject: is 'E=mc2' part of relativity, or some other work by Einstein?

I've searched the MadSci archives.  An answer to question with ID# 
1010523569.Ph from a professor in Stockholm says that E=mc2 is part of Special 
Relativity, but an answer to question with ID# 956282795.Ph from a retired 
engineer says that the equation comes from a paper by Einstein called "Does the 
Inertia of a Body Depend Upon Its Energy Content", published 1905.  Okay -- I 
know that Einstein published in 1905 on relativity, Brownian motion, and the 
photoelectric effect and the encyclopedia says he published 3 major papers that 
year; but the website for the museum at Einstein's house in Bern 
(http://www.einstein-bern.ch/index.php?lang=en&show=aeg) says he published 5 
(plus his dissertation).  Maybe this is one of the other two that the 
encyclopedia doesn't mention?  If E=mc2 wasn't in the paper on relativity, does 
that mean it is not part of relativity?  Or did Einstein publish more than one 
paper on relativity that same year, and is this paper on Inertia part of 
Special Relativity?

Re: is 'E=mc2' part of relativity, or some other work by Einstein?